Ecological and genetic effects on demographic processes: pollination, clonality and seed production in Dithyrea maritima

The relative importance of ecological and genetic factors in regulating the demographic processes of small populations is unknown for most rare plants. Dithyrea maritima (beach spectacle pod; Brassicaceae) is a rare, rhizomatously spreading, and self-incompatible herbaceous perennial endemic to coastal sand dunes of southern California. Low seed production in this species may be caused by insufficient pollinator visits, which may be exacerbated by competition for pollinator visits from non-native plants that have invaded the coastal dunes. I tested this ‘ecological’ hypothesis by removing flowers of Cakile maritima and Carpobrotus spp. from three experimental plots on San Nicolas Island. A second possible limitation on seed set is low diversity of genets within subpopulations, which could lead to scarcity of compatible mates. I tested this ‘genetic’ hypothesis by assigning ramets to clones using isozymes, and by relating clonal diversity within populations to seed set. Removal of non-native plants had no detectable effect on pollination service to D. maritima or on seed set, and seed set was unrelated to natural variation in pollination service among populations within a single year. In contrast, clonal diversity within a 10 m² patch was a strong predictor of seed set. Hence a genetic factor explains spatial variation in seed set on San Nicolas Island. On larger spatial and temporal scales, however, pollination service also affects patterns of seed set: a shift in pollination from flies in 1998 to bees in 1999 probably caused a corresponding increase in seed set across San Nicolas Island, while extremely low seed set at another site (San Miguel Island) is probably caused by a virtual absence of pollinators there.     

Fruiting failure and limited recruitment in remnant populations of the hawkmoth-pollinated tree Oxyanthus pyriformis subsp. pyriformis (Rubiaceae)

Plants with highly specialized pollination systems may be particularly vulnerable to the effects of habitat fragmentation. The sub-canopy tree Oxyanthus pyriformis subsp. pyriformis has deep tubular flowers (c. 90 mm in length) that are specialized for pollination by long-tongued hawkmoths. Existing natural populations of this taxon appear to be confined to two suburban habitat fragments in the city of Durban, South Africa. Breeding system experiments showed that the trees are self-incompatible and thus completely reliant on pollen vectors for sexual reproduction. Hawkmoths were rarely observed to visit flowers, despite intensive monitoring over four seasons from 1997 to 2003. Fruit set as determined from examination of more than 150,000 flowers at the two sites was extremely low (0.04% and 0.07% of flowers), but increased to more than 70% in flowers that were hand-pollinated with pollen from another tree. This >1000-fold increase in the likelihood of fruit production following pollen-supplementation indicates that trees experience severe pollen-limitation of fruit set. Natural fruit set is so low that only a few dozen fruits were recorded in each population during two years of monitoring. This is of concern as O. pyriformis trees are dependent solely on seeds for recruitment. Demographic surveys showed that remaining natural populations have fewer saplings than adult trees and only two seedlings for every adult tree. The long-term viability of reintroduced populations of O. pyriformis is also in doubt, as we observed an almost complete lack of recruitment in a population that was established in a seemingly suitable forest site 20 years ago. Regular hand-pollination and, in some instances, further planting of saplings, may be the only way to safeguard these populations.     

How important is clonal recruitment for population maintenance in rare plant species?: the case of the narrow endemic cactus, Stenocereus eruca, in Baja California, México

Stenocereus eruca is a postrate columnar cactus whose regeneration seems to occur mainly through clonal propagation. It is a narrow endemic species of the Sonoran desert in Baja California Sur and currently considered as threatened under Mexican legislation. In this paper we describe the demography of ramets in four populations along its distribution range and the demography of genets in one population during a 3-year-study period in order to evaluate its conservation status. We also analyze the relative contribution of sexual reproduction and clonal propagation to population maintenance and provide guidelines for the formulation of conservation programs. Elasticity analyses were used to explore the relative contribution of sexual and clonal recruitment to projected population growth rate (λ). During the three years of study, regeneration occurred only through clonal propagation while sexually derived seedlings were not detected within or outside the permanent plots. Our demographic data showed that the four population of S. eruca are in equilibrium (λ ≈ 1), and elasticity analyses showed that the relative contribution to λ of clonal recruitment was larger than sexual recruitment, at least during the analyzed ecological time scale. Simulations showed that removing sexual recruitment had a minor impact on λ, but the absence of clonal propagation alone was sufficient to keep below unity. We propose the establishment of at least one reserve with adequate protection from human disturbance to conserve S. eruca.     

Effects of edaphic factors on the tree stand diversity in a tropical forest of Sierra Madre del Sur, Mexico

Two sites with similar environmental parameters, except for the edaphic factor, were selected in the mountainous tropical forest of southern Mexico. Site 1 was established on an Alisol; site 2, on a Phaeozem. Representative soil profiles were examined on each of the sites, and topsoil was sampled on a regular grid pattern. The soil of site 2 was richer in organic matter and major nutrients and had a less acid reaction than the soil of site 1. The species diversity of the trees at site 2 (30 species) was higher than that at site 1 (17 species). The species compositions of the trees were different on the two soils: there were only six species in common for both sites. The coefficients of species similarity on the sites were low. We concluded that the presence of different soils within the same type of forest ecosystem increases its ??-diversity. The examination of edaphic preferences of the species showed that Alstonia longifolia and Thouinidium decandrum preferred rich soils, Inga punctata and Ocotea sinuata preferred poor soils, and Cupania dentata and Hamelia patens did not display preferences in the studied range of soil properties. Thus, the spatial variability of the soil properties affect the spatial pattern of tree species in the studied tropical forest ecosystems.     

Conservation of bats in suburban landscapes: roost selection by Myotis yumanensis in a residential area in California

Protection of roosting habitat is essential to the conservation of bats in human-dominated landscapes. To help define bat roosting needs in suburban settings, we used radio telemetry to locate day roosts of a common North American species (Myotis yumanensis) within a residential area in California. Between June and August 2000, we tracked 16 bats to 20 roosts in two buildings and 18 trees. We used multiple logistic regression to assess roost selectivity at multiple spatial scales. Of 15 tree, plot, and site characteristics considered, only three helped distinguish roosts from random comparisons: tree diameter, distance to water, and forest cover. Myotis yumanensis preferred large trees (mean diameter 115 cm), and roosted only in the five species of largest mean diameter (Sequoia sempervirens, Pseudotsuga menziesii, Quercus agrifolia, Quercus lobata, and Acer macrophyllum). At the site level, these bats selected roosts that were close to water and had substantial forest cover in the surrounding 100-m radius. Unlike other North American bats, they often roosted in live trees (89% live). Relatively high roost fidelity (mean 4.8 days) and large travel distances between consecutive roosts (mean 1130 m) and between capture sites and roosts (mean 2007 m) may indicate a greater degree of roost limitation at this site versus other research sites. We recommend the preservation of large trees and forested parkland, particularly along stream corridors, to help maintain bat populations in urbanizing landscapes.     

Breeding system, genetic diversity and clonal structure in the sub-alpine forb Rutidosis leiolepis F. Muell. (Asteraceae)

Genetic markers, controlled pollinations and chromosome analysis were used to examine the breeding system, clonal structure, genetic diversity and cytological complexity of populations of the endangered sub-alpine forb Rutidosis leiolepis. Results show that R. leiolepis: (1) has a strong sporophytic self-incompatibility system; (2) exhibits significant clonality and that the importance of vegetative reproduction increases at higher altitudes; (3) is genetically diverse, but that variation within populations decreases and differentiation among populations increases with altitude; and (4) is diploid with 2n=22 throughout its geographic range. Based on these results, low altitude populations around Cooma and Happy Valley should be made priority areas for in situ conservation in the Species Recovery Plan currently being developed by the New South Wales National Parks and Wildlife Service because they exhibit the most sexual reproduction and highest levels of genetic variation within the species. They may also be demographically more viable in the long term, having larger effective population sizes and less likelihood of mate limitation due to low S allele richness than high altitude populations. Sampling strategies for ex situ conservation should vary from large collections within populations at low altitudes to smaller collections spread across populations at higher altitudes where more of the genetic diversity is partitioned among sites. This should give maximum representation of the species' gene pool for minimum sampling effort.     

Comparative population structure and reproductive biology of the critically endangered shrub Grevillea althoferorum and two closely related more common congeners

Grevillea althoferorum is a critically endangered, sprouting shrub known from two disjunct populations within the South-West Botanical Province of Western Australia. This study compares the conservation biology of G. althoferorum and two closely related but more common congeners, the non-sprouter G. rudis and the sprouter G. synapheae subsp. pachyphylla in order to determine whether there are differences in reproductive and ecological attributes that might explain why G. althoferorum is rare. In contrast to the more common species, neither population of G. althoferorum exhibited evidence of seedling recruitment. However, the northern population was confirmed to be clonal and was actively recruiting from root suckers. Both populations of G. althoferorum were found to have reduced amounts of viable pollen on stigmas in comparison with the other species. The fruit set at the southern population of G. althoferorum was considerably lower than that found for the common species, with only 0.15% of flowers setting fruit and no fruit was produced in the northern population. In addition no evidence of a soil seed bank was found for either population of G. althoferorum, but G. rudis and G. synapheae subsp. pachyphylla both had soil stored seed which germinated following treatment with aqueous smoke solution. Sexual recruitment at both populations of G. althoferorum was absent, and reproduction appears to be predominantly clonal in the northern population. Management strategies for G. althoferorum should therefore focus on the protection of adult plants from accidental destruction.     

Predicting reproductive success of insect- versus bird-pollinated scattered trees in agricultural landscapes

Scattered trees are set to be lost from agricultural landscapes within the next century without sustained effort to increase recruitment. Thus, understanding the reproductive dynamics of scattered tree populations will be critical in determining how they can contribute to population restoration. The distance between conspecifics should be a key predictor of reproductive success, as more isolated trees are expected to receive fewer pollinator visits and experience increased transfer of self-pollen during longer pollinator foraging bouts. Further, isolation effects should be greater in species with less mobile pollinators. Here we contrast the effects of plant isolation on reproductive success of two species of eucalypt “paddock trees”, Eucalyptus camaldulensis and Eucalyptus leucoxylon, with insect- and bird-pollination, respectively. Seed production was not affected by tree isolation in either the insect- or bird-pollinated species and once outliers were removed, neither was there an effect on germination rate. As somatic mutations may bias outcrossing rate estimates, we initially screened our microsatellite markers for mutations but found no variation in microsatellite profiles throughout the canopy of trees. Individual outcrossing rates did not decline with increasing tree isolation in either the insect- or bird-pollinated species, though there was considerable variation in these rates at large distances, suggesting that pollination becomes unreliable with increasing tree isolation. We found that pollination distances have likely increased in tree species in agricultural landscapes, and that this may be facilitated by introduced honeybees in the case of E. camaldulensis. We therefore suggest that even isolated trees of these species produce seed of sufficient quantity and quality to contribute to population restoration.     

Genetic consequences of using seed mixtures in restoration: A case study of a wetland plant Lychnis flos-cuculi

Sowing with seed mixtures is a common practice in restoring species-rich communities in areas with impoverished species pools. The potential genetic consequences of using these mixtures, however, are poorly understood and often not considered in practical restoration. We investigated genetic diversity, inbreeding and genetic structure of samples collected from 26 populations of the common wetland plant species Lychnis flos-cuculi in an agricultural region in Switzerland. Some of these populations were natural, while others had been sown several years ago. This enabled us to compare the genetic composition of populations of indigenous origin with those originating from commercially produced seed mixtures. Gene diversity and allelic richness were similar in natural and sown populations. In contrast, inbreeding coefficients were three times higher in sown than in natural populations. The sown populations were genetically distinct from the native populations. We distinguished two homogeneous gene pools that presumably originated from different source populations used to produce seed mixtures. The use of commercially produced seeds may alter the genetic diversity and structure of plant populations. The observed higher inbreeding coefficients of sown populations could lead to reduced population viability. To restore genetically diverse populations, the seeds for further propagation should be collected from numerous individuals in large and non-isolated populations nearby restored sites. Ex situ stocks for the production of commercial seed mixtures should only be propagated for a few generations to avoid negative effects such as inbreeding or loss of local adaptation.     

Seeds capture the diversity of genetic resource collections of <Emphasis Type="Italic">Malus sieversii</Emphasis> maintained in an orchard

Many species in genebank collections are maintained vegetatively either as in vitro cultures or as plants in the field or greenhouse. In these cases, individual genotypes (cultivars) are the focus of conservation. In crop wild relatives, where the value of an accession is in the heterogeneity of segregating genotypes, seeds may be the most representative form of conservation. We used two sets of field-planted Malus sieversii apple trees that originated from seeds collected from two wild populations in Kazakhstan as a model system to determine if seeds from hand-pollinated crosses could be used to represent the allelic diversity of the parent trees in a genebank orchard. A crossing design was developed that used each of the selected trees from the two Kazakhstan collection sites as mothers and also as fathers in the form of bulked pollen pools. The sets of offspring from these crosses were genotyped using microsatellite markers. Paternity analyses revealed the percentage of offspring that was derived from each of the parent trees. We also determined the contribution of each parent to the fertilization events from the pollen pools. Although there were some unintended pollination events (fertilization by trees in unexpected pollen pools) and unequal contribution of pollen parents within pollen pools, we demonstrated that the seedlings effectively captured the allelic frequency and diversity of the parents. A seed collection strategy is the most efficient way to conserve the diversity of crop wild relatives even in collections typically conserved as individual clones.     

Toward the restoration of a sustainable population of a threatened aquatic plant, Nymphoides peltata: Integrated genetic/demographic studies and practices

We provide a brief review of practices and relevant studies for restoration of Nymphoides peltata (yellow floating heart, Asaza), a distylous floating-leaf clonal plant, in Lake Kasumigaura, Japan to develop a model of integrated genetic and demographic conservation for threatened plants. Several theoretically expected issues, such as sudden extinction of small populations with low genetic diversity, limited seed production in small-sized local populations, and significantly high heterozygosity in adults that have survived environmental change, were ascertained through integrated studies on demography with discrimination of genets and genetics using highly polymorphic genetic markers. Investigation of genetic properties of the remnant soil seed bank suggested that the seed bank could potentially restore genetic diversity, although the fitness reduction of seed banks caused by inbreeding could affect the success of restoration. As a result of restoration efforts, increases in the number of local populations and genets in the Lake Kasumigaura metapopulation have led to population recovery.     

Remnant sugar maple (Acer saccharum subsp. skutchii) populations at their range edge: Characteristics,environmental constraints and conservation implications in tropical America

Relationships between environmental conditions and persistence of populations at edges of ranges should be useful for predicting consequences of climate change. We characterized environmental conditions of six disjunct sites in Mexico and Guatemala that contain all known relict populations of the most southern subspecies of sugar maple, cloud forest sugar maple (Acer saccharum subsp. skutchii). We also sampled abundance and basal area of all tree species, recording 164 species, 92 genera (61% tropical), and 54 families at these sites. Temperate genera decreased in number from north to south, but mixtures of temperate and tropical species were co-dominant with cloud forest sugar maple at all sites. For all species, basal area was 24–52 m² ha^?1 and density was 990–2986 trees/ha at the six sites. Cloud forest sugar maple comprised 7–43% of total basal area and 1–16% of total densities at each site. Populations of cloud forest sugar maple currently are vulnerable to environmental change. Anthropogenic disturbance is negatively affecting four populations, and regeneration is successfully occurring in only two sites. As a result, densities and basal area are much reduced compared to more northern temperate populations. NMS-ordination indicated that elevation and hurricane frequency are major environmental constraints related to abundance. Maple recruitment is associated with short hurricane return intervals that maintain higher elevation cloud forests in states conducive for regeneration. We establish the conservation status of cloud forest sugar maple at the southern end of its range relative to expected climate change and propose this subspecies be included in the IUCN-Red List.     

Air-pollution-induced foliar injury to natural populations of jack and white pine in a chronically polluted environment

Air-pollution-induced foliar injury was determined for natural populations of jack pine (Pinus banksiana) and white pine (P. strobus) on Lake Michigan sand dunes in Indiana. Chlorotic mottle and tip necrosis were found in all populations and one or both symptoms appeared in most trees. However, considering the proximity of the populations to pollution sources, foliar injury levels were notably low. Despite a limited range of individual tree injury for mottle, necrosis, needle retention, and needle length, populations within each species differed significantly (P < 0.05). Juvenile trees showed greatest injury. Symptom expression in both species was related to qualitative site rankings for 03 and S02 exposure in nested analysis of variance, even when tree-to-tree variation was controlled. In both species, mottle increased with 03 ranking and tip necrosis with SO₂ rank, but relationships were not always monotonic and showed interactions with site factors. For most trees, tip necrosis affected less than 1 % of the needle length of one-year needles, and mottle covered under 2% of needle surface. The low visible injury range is hypothesized to result from genetic selection favoring genotypes tolerant of the lowered air quality that has characterized the region for the past 70 yr.     

Enchytraeid and earthworm communities along a pollution gradient near Olkusz (southern Poland)

The effect of heavy metal pollution on Oligochaeta (Enchytraeidae and Lumbricidae) populations was studied along a pollution gradient in vicinity of Olkusz (southern Poland). The study sites, which differed in metal concentrations in the humus layer, were established in mixed-pine forests 3.5 km, 2.5 km, 3.9 km, 7.9 km and 31.9 km (reference site) from the source of pollution (zinc smelter). Enchytraeid and earthworm population density and species composition were determined from soil sampled four times from the study sites. Enchytraeidae populations consisted of nine genera and 18 species. The dominating enchytraeid species in all study sites was Cognettia sphagnetorum (approx. 90%), except for the most polluted site, where Enchytraeus, Fridericia and Henlea were the most common species diversity and heterogeneity were the highest in the most polluted site. The highest mean densities were found in the reference site (16,333 individuals m^?2) and lowest in the most polluted site (3932 individuals m^?2). Earthworm populations consisted of three epigeic species, and the most abundant one was Dendrobaena octaedra. Earthworms densities in all sites sampled were low. The concentrations of Zn, Pb and Cd in: humus layer, and in enchytraeids and earthworms, were the highest for the most polluted site and decreased with distance from pollution source. Density of Enchytraeidae and body loads of metals in Enchytraeidae and Lumbricidae can be employed for biomonitoring.     

Recruitment and regeneration in populations of an endangered South Iberian Tertiary relict tree

The southern Iberian Peninsula is one of the most important refugia of Tertiary relict plant taxa in Europe. Under the present summer-dry climate, relict populations may experience a severely reduced regeneration. We studied the demographic structure, seed set and initial recruitment in relict populations of the endangered tree Frangula alnus subsp. baetica (Rhamnaceae) to evaluate its regeneration potential under the present environmental conditions. Populations are restricted to small riparian forests of Southwest Spanish and North Moroccan mountain ranges. The distribution of fruit crop sizes was highly left-skewed, and a few old trees produced the large bulk of the population seed pool. Bird-mediated seed dispersal appeared inefficient and post-dispersal seed predation by mice was high. Secondary seed transport by elevated creek water flow after winter rains modified the primary seed dispersal, but in consequence most seeds germinated on recently formed sandbanks where seedlings experienced reduced initial growth and survival. The most important mortality factor was desiccation, followed by herbivory. None of 1144 monitored seedlings survived for 2 years. The demographic survey through five populations indicates that drought periods may cause temporal regeneration bottlenecks. Moreover, over the last two decades populations have experienced increasing regeneration problems. Two causes are suggested: (1) browsing pressure from introduced game animals, and (2) the impact of torrential water flow peaks after heavy winter rains, exacerbated by large-scale vegetation slashing in surrounding cork oak forests. We discuss conservation strategies for this and other relict tree species that account for the pecularities of their habitat within the Mediterranean.     

Conservation genetics and implications for restoration of Hemigenia exilis (Lamiaceae), a serpentine endemic from Western Australia

Hemigenia exilis (Lamiaceae) is a rare plant endemic to serpentine soils of the Goldfields of Western Australia. The species was presumed extinct until 1995, when it was re-discovered on a nickel ore deposit. To delineate the origin and extent of seed collection for rehabilitation after mining, and to identify the impact of removing one population due to mining, we assessed level and partitioning of genetic variation and differentiation. Twelve populations were sampled for DNA fingerprinting using the random amplified polymorphic DNA (RAPD) technique. Ten primers produced 89 bands, 97% being polymorphic. Genetic diversity within populations ranged from 0.197 to 0.409, averaging 0.38 at the species level, which is high compared with most other endemic species. Heterozygosity within populations ranged from 0.355 to 0.431, averaging 0.27 over the species. AMOVA partitioned over 80% of the total variation within populations. Multidimensional scaling revealed weak but significant differentiation into a northern and southern provenance. Despite selective sampling, the genetic data provided useful information for the management of Hemigenia exilis. For restoration, seed should be collected from a range of habitats of several populations, while keeping the two provenances separate. This strategy is likely to maintain high genetic diversity and locally adapted populations.     

Natural history collections and the conservation of poorly known taxa: Ecological niche modeling in central African rainforest genets (Genetta spp.)

Natural history collections are crucial resources for conservation biology, particularly given the development of the ecological niche modeling (ENM) approach. We combined ENM with taxonomic investigations to address ecological, geographic, and phenotypic variation in the poorly known central African rainforest genets (Genetta cristata, Genetta servalina, Genetta victoriae) to provide new insights into their conservation status. Taxonomic identification was based on four discrete morphological characters. ENMs were developed using the Genetic Algorithm for Rule-Set Prediction (GARP), 10 environmental data layers and 310 georeferenced localities extracted from 667 museum specimens and 22 literature sources. Re-assessed taxonomic identifications allowed us to expand significantly the known range and ecological limits of the three genets. We suggested limited hybridization between G. cristata and G. servalina, in a zone of sympatry likely to cover central Cameroon, northwestern Gabon and Congo. ENM showed that almost all known occurrences were connected geographically by suitable ecological conditions, suggesting continuous potential distributions between supposedly isolated populations of the three genets. Our investigations indicated that G. cristata is distinct from G. servalina in morphology, geographic ranges and ecological niches, indicating species status for G. cristata, which, as such, should be the subject of appropriate conservation attention. Areas of predicted connectivity and actual zones of occurrence falling outside current forest cover should be surveyed to re-assess the status of the rainforest genets. Our study shows that combining ENM and taxonomic investigations can substantially improve data utilization from natural history collections, especially in the case of poorly known species.     

Location of roosts of the lesser long-eared bat Nyctophilus geoffroyi and Gould's wattled bat Chalinolobus gouldii in a fragmented landscape in south-eastern Australia

The location of roosts of two species of vespertilionid bats, the lesser long-eared bat (Nyctophilus geoffroyi) and Gould’s wattled bat (Chalinolobus gouldii), was investigated in a remnant vegetation-farmland mosaic and adjacent floodplain forest in south-eastern Australia. A total of 45 individuals of N. geoffroyi and 27 C. gouldii were fitted with radio transmitters, which resulted in the location of 139 and 89 roosts respectively. Selection of roosting habitat showed both inter- and intra-specific differences. At the landscape level, locations of roosts used by male and female N. geoffroyi differed markedly. Most males roosted in the farmland mosaic within 3 km (mean 1.9±2.9 km) of where they were captured while foraging in remnant vegetation. In contrast, roost sites of females were predominantly in the floodplain forest, 6-12 km from their capture site in farmland (mean for all females, 6.7±2.9 km). All maternity roosts were in the extensive floodplain forest, 4-10 km from foraging areas. Distances moved by this species were greater than previously recorded and further than predicted by flight morphology. Most C. gouldii roosted in the floodplain forest, 4-10 km from their capture site (6.9±1.6 km). Within the floodplain forest, both species roosted in areas that had higher densities of hollow-bearing trees than generally available; dead hollow-bearing trees for N. geoffroyi and large, live trees for C. gouldii. The scale of movements undertaken by these species means that they can obtain resources from multiple landscape elements. Both species used different habitats for roosting and foraging despite the energetic costs of commuting relatively large distances. Conservation of bat populations in rural environments needs to be considered at the landscape scale, with particular attention to identifying landscape elements that provide key resources.     

Genetic data confirms field evidence for natural breeding in a wild taro population (Colocasia esculenta) in northern Queensland, Australia

Taro (Colocasia esculenta) is a vegetatively propagated, starchy root crop cultivated in tropical to temperate regions of the world. Wild forms of taro are distributed from India to southern China, Australia and Melanesia. They are widely known wild food or fodder sources, including in Aboriginal Australia, so it is unclear to what extent wild populations have been dispersed by humans, or naturally via insect-borne pollen and seed dispersal by birds or other animals. In Australia, pollinators and seedlings of taro have not been reported, and a key question is whether or not the wild taro there can breed naturally. Here we report field observations of flowering, fruit set, and an insect pollinator (Colocasiomyia, pupal stage), in a historically significant wild taro population at Hopevale in northern Queensland. The observed pupa is congeneric with two pollinating fly species that have a highly specialised, probably coevolutionary, relationship with taro in neighbouring Papua New Guinea. The field observations suggested the possibility of natural breeding at Hopevale. By analyzing microsatellite diversity within the Hopevale taro population, we found high genetic variation overall, indicative of multiple founding individuals. Two sublocations showed low genetic diversity and strongly negative inbreeding coefficients, consistent with predominantly clonal (vegetative) reproduction. A third sublocation showed high genetic diversity and a weakly negative inbreeding coefficient, indicative of sexual reproduction. This difference between sublocations may relate to microenvironmental conditions that favour seedling establishment in some parts of the site. The data constitute the first demonstration that natural breeding and population spread occurs in Australian wild taro.     

Lizard microhabitat and fire fuel management

For many species, dead vegetation is important microhabitat necessary for survival and reproduction. We compared the use of three categories of trees: living, dead standing and dead prone, within and among four species of phrynosomatid lizard (Sceloporus undulatus, Sceloporus graciosus, Urosaurus ornatus, and Uta stansburiana) on the Colorado Plateau during 1990, 1992 and 2000. All four species used dead trees (both prone and standing) more frequently than live trees, despite an opposite pattern of availability. U. ornatus used dead standing more often than dead prone trees, reflecting this lizard's arboreal nature. Tree use did not differ among lizard species, and the lizard species by tree category interaction was not significant. Current policy mandates the removal of dead vegetation and debris on US Federal lands as basic maintenance in order to decrease fire risk. Active removal of “fuel” may limit the local distribution, abundance, and diversity of these lizards, which include dead trees in their microhabitat for shelter, perching, foraging, courting, and defending territories.