Inbreeding and small population size reduce seed set in a threatened and fragmented plant species, Lupinus sulphureus ssp. kincaidii (Fabaceae)

Willamette Valley upland prairie in western Oregon, USA, has been reduced to less than 1% of its original historic range following European settlement in the 1850s. Lupinus sulphureus ssp. kincaidii (Kincaid's lupine), a threatened species and the primary larval host plant of the endangered Icaricia icarioides fenderi (Fender's blue butterfly), was historically a panmictic metapopulation. Habitat fragmentation may be causing many of the Kincaid's lupine colonies to display typical symptoms of inbreeding depression, such as low seed production. Hand outcrosses on bagged inflorescences significantly increased seed set and seed fitness compared to open pollination and within-colony pollen treatments. Natural seed set was positively correlated with an increase in the number of Kincaid's lupine patches, suggesting that population size limits seed set. An increase in fruit set was positively correlated with Kincaid's lupine raceme number, raceme density, and the number of lupine patches, demonstrating that floral display and population size increase pollinator service. Restoration of Kincaid's lupine populations should consider measures that lessen the effects of inbreeding depression, especially in small, isolated populations, for the long-term persistence of the species.     

Effect of forest fragmentation on fruit and seed predation of the tropical dry forest tree Ceiba aesculifolia

Forests fragmentation reduces the density of natural plant populations forming patches of the remaining individuals. One of the biotic interactions that can be affected by forest fragmentation and is poorly studied is seed predation. We determined the effects of forest fragmentation on seed and fruit predation in Ceiba aesculifolia by comparing trees in continuous forest with trees in fragmented forest. We compared the following variables: (a) frequency of fruit predation by Collie’s squirrel (Sciurus colliaei) in each habitat; (b) frequency of the cotton-staining bug seed predator (Dysdercus, Orden Hemiptera) in each habitat; (c) the effect of seed predation on germination frequency and time; and (d) the effect of different life stages of Dysdercus on seed viability. In continuous habitat, 100% of the trees presented fruits with squirrel predation while only 34% of trees in fragmented habitats presented fruit predation. In continuous forest 27% of the trees contained fruits with the seed predator Dysdercus, while only 2% of the trees in fragmented forest presented Dysdercus. The initial weight of damaged seeds was greater than seeds that were not damaged indicating that seed predators select heavier seeds to feed upon. Frequency of seed germination was affected by different life stages; pre-adults decreased germination significantly more than nymphs and adults. Seed predation significantly increased the time it took for germination to occur. Our study shows that forest fragmentation significantly affects predation patterns of squirrels and cotton-staining bugs. Reduction of natural seed predators in forest fragments may have long-term consequences on forest structure and diversity.     

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.     

Effects of forest fragmentation, anthropogenic edges and fruit colour on the consumption of ornithocoric fruits

We investigated effects of fruit colour (red, black or white), habitat (anthropogenic edges and forest interior) and fragment size on the removal of artificial fruits in semideciduous forests in south-east Brazil. Eight forest fragments ranging from 251 to 36,000 ha were used. We used artificial fruits, which were placed on shrubs between 1 and 2 m in height and checked after 48 and 96 h for peck marks in the fruits. All three variables affected the probability of consumption of our fruit models. Red and black fruits were statistically more pecked than the white fruits. The probability of fruit consumption was lower in the interior than at the edge and less in small than in large fragments. However, the decrease fruit consumption in small compared with large fragments was more accentuated for red and black fruits than for white fruits. Our results show that habitat reduction and edges affect the chances of a fruit being eaten by birds, which may ultimately affect plant fitness in forest fragments.     

Effects of habitat fragmentation on pollen flow and genetic diversity of the endangered tropical tree Swietenia humilis (Meliaceae)

Fragmentation of tropical forest represents a major threat to some tree populations by reducing local population size and gene flow from other populations. Both processes can decrease outcrossing rates and genetic variation in remnant stands. Despite these risks, some tree species have pollen vectors that mitigate these negative consequences for fragmented populations. In this paper, we assess both pollen flow and diversity of pollen sources in continuous forest and isolated stands of Swietenia humilis, a tropical tree species pollinated by small insects. Using seven nuclear microsatellite markers, we test the hypothesis that genetic diversity and the number of pollen donors are lower in remnant populations. Results show that allelic richness of seeds is lower in isolated populations (6.1 vs. 8.3 alleles per locus), even though adult populations do not show this difference.Pollen pool structure is greater in isolated patches (Φ_Iso = 0.26) than in continuous forest (Φ_For = 0.14), which yields estimates of the average effective number of pollen donors (N_ep) of 1.9 and 3.6 respectively. In addition, estimates of number of sires per mother indicate that isolated trees have half the number of pollen sources (4.98) than trees in the forest (9.8). Although extensive pollen movement (>2000 m) was recorded on both habitat conditions, indicating that fragmented patches are not isolated from pollen-mediated gene flow, this extensive pollen flow among trees in fragmented landscapes may not serve to counteract deleterious reproductive and genetic consequences of habitat fragmentation.     

种子引发对盐胁迫下高粱种子萌发及幼苗生长的影响

以“Tx623A”ד89-363”(Sb1, 耐盐性较弱)和“黑30A”ד大粒早”(Sb2, 耐盐性较强)2 个高粱杂交组合为试验材料, 利用100 mmol·L^-1?NaCl 溶液对种子进行引发处理。采用营养液沙培试验, 设4 个NaCl 浓度(0、50 mmol·L^-1、100 mmol·L^-1和150 mmol·L^-1)模拟盐胁迫, 研究种子引发处理对盐胁迫下高粱种子萌发及幼苗生长的影响。结果表明: 随着盐胁迫强度增加, 无论经引发处理还是未经引发处理2 个高粱杂交组合种子的出苗时间均明显延迟, 出苗率和成苗率下降, 幼苗生长受到抑制, 物质积累减少。同等盐胁迫强度下,引发处理与未引发处理相比, 种子出苗时间缩短, 出苗率和成苗率提高, 幼苗地上部分干、鲜重和地下部分干、鲜重增加, 光合色素含量升高, Na⁺/K⁺值显著降低。由此得出, 种子引发处理可以不同程度地促进盐胁迫下高粱种子萌发, 减轻盐胁迫对幼苗的伤害, 促进幼苗生长, 提高耐盐性; 耐盐性不同的品种引发效果存在差异, 对耐盐性较弱的品种引发效果更好。     

Reduced seed production, inbreeding, and pollen shortage in a small population of a threatened tree, Magnolia stellata

We investigated how genetic factors and pollen shortage affect seed production in a small population of Magnolia stellata, a threatened insect-pollinated tree. We used microsatellite and manual pollination techniques, and compared a small population to a large one. Compared to the large population, the small population showed low allelic variation and had an F_IS significantly greater than 0 in adults, indicating that genetic deterioration, including genetic drift and inbreeding, may have occurred in adults. Manual self-pollination lowered seed production relative to manual cross-pollination to a different extent between populations: δ (the magnitude of inbreeding depression due to self-fertilization) was lower in the small population than in the large population. However, under natural pollination, the estimated embryo mortality rates after ovules self-fertilized were similar between the two populations because the primary selfing rate was higher in the small population. The ovule mortality rate due to pollen shortage and that due to factors independent of pollen shortage and selfing were both approximately 10% higher in the small population, suggesting that pollen transfer may have decreased and genetic deterioration effects may have increased in that population. These factors reduced seed production in the small population (female reproductive success = 0.3%) compared to the large population (2.6%). Our results suggest that seed production in the small population of M. stellata is strictly limited by elevated pollen shortage, selfing, and genetic deterioration in adults, which accelerate the risk of extinction.     

Effects of forest fragmentation on two sister genera of Amazonian rodents (Myoprocta acouchy and Dasyprocta leporina)

Because agoutis (Dasyprocta sp.) and acouchies (Myoprocta sp.) are the most important dispersers of several large-seeded Amazonian trees, knowing their responses to forest fragmentation is essential and urgent. But until now, there was no study showing their population trends in Amazonian land forest fragments. The present study was conducted at the Biological Dynamics of Forest Fragments Project, Central Amazon, Brazil. Eleven sites (three fragments of 1 ha, three of 10 ha, two of 100 ha and three sites of continuous forest) were surveyed between 2003 and 2005. Agoutis and acouchies were systematically counted at each site through standard transect censuses and their densities were estimated with DISTANCE 4.1. Overall, I walked 100 km, and encountered 136 acouchies and 35 agoutis. Fragmentation had a significant negative effect on acouchies and a significant positive effect on agouti densities. Acouchy density was 0.64 ± 0.09 inds./ha in continuous forests and 0.07 ± 0.07 inds./ha in 1-ha fragments. On the other hand, agouti density was 0.16 ± 0.05 inds./ha in continuous forests and 0.71 ± 0.24 inds./ha in 1-ha fragments. This study is consistent with the idea that in fragments, larger species of mammals are initially less affected by forest fragmentation than smaller ones. More critical to conservation is the fact that acouchies, which were negatively affected by fragmentation, are restricted to the core region of the Amazonian rainforests. Continued fragmentation of Amazonian forests should have vast negative consequences for the genus.     

Extrinsic and intrinsic controls on the distribution of the critically endangered cress, Ischnocarpus exilis (Brassicaceae)

Ischnocarpus exilis, a critically endangered cress, persists in one small population in a 1m² section of a limestone tower in the South Island, New Zealand. The importance of intrinsic (seed production, dispersal ability and habitat specificity) and extrinsic factors (weed competition) acting to restrict the distribution of this threatened species were investigated with a field experiment, demographic monitoring and soil seed bank analysis. I. exilis is not confined to its present site because of high habitat specificity, but rather is limited by low seed production and limited dispersal as well as by competition with invasive weeds. Conservation management of this critically endangered species should focus on controlling weeds and on establishing new populations in suitable weed-free habitat.     

Development, fatty acid composition, and storage of drupes and seeds from the endangered pondberry (Lindera melissifolia)

Pondberry (Lindera melissifolia [Walt.] Blume: Lauraceae) is an endangered, dioecious, clonal shrub that grows in bottomland hardwood forests in the southeastern United States. Prior work has emphasized vegetative reproduction associated with the clonal nature of this species. Little has been published about the early morphological and biochemical characteristics of the fruit as they mature. Fruits, drupes originating from the axillary buds, were collected every 30 days after anthesis and examined for seed structure development and fatty acid composition of the fruit and seed. Sixty days after anthesis, fruits had not formed an organized embryo/cotyledon, weighed 0.1 ± 0.001 g, and measured 7.1 ± 0.04 mm × 4.3 ± 0.03 mm. Ninety days after anthesis, a complete seed had formed within the drupe. Of the total drupe weight (average 0.23 ± 0.01 g), the seed comprised 33% of the mass gained from 60 days after anthesis. Overall composition of the seed and pulp lipids changed significantly over the course of development. Myristic, palmitic, steric, oleic, linoleic, and linolenic fatty acids were revealed by the lipid analyses. Lauric acid was not found in any of the early seed lipid samples but it increased in quantity as seed matured to become the dominant fatty acid in this tissue. Conversely, pulp contained only small amounts of lauric acid; its fatty acid profile was dominated by oleic acid. Fully hydrated seeds stored well for 16 months at both 4 °C and −2 °C. Although drying had a deleterious effect on germination when dried seeds were conventionally stored at 4 °C, seeds that had been dried for 24 h to a moisture content of 8.6% were successfully stored in liquid nitrogen.     

Age and size at first reproduction in the commercially exploited red coral Corallium rubrum (L.) in the Marseilles area (France, NW Mediterranean)

Among species life-history traits, size and age at first reproduction are particularly relevant to design meaningful conservation plans. The main goal of this study was to define the size at first reproduction of colonies of the precious red coral Corallium rubrum (L.) and determine their age, thanks to a new reliable method. Sampled colonies come from two sites at 40 m depth on the French Mediterranean coast near Marseilles. Furthermore, we report trends in reproduction parameters in relation to colony size. The smallest fertile colonies (<30 mm height class) were on an average 24.0 mm in height and 3.6 mm in basal diameter: these colonies were on an average between 7 and 10 years. The reproductive effort, i.e., percentage of gravid polyps per colony, was higher in large (>50 mm in height) and medium size colonies (30-50 mm) than in small ones (<30 mm). Our results indicate that management strategies for the conservation of red coral should lead to increase the abundance of large colonies to guarantee a good reproduction output. Suggested measures are minimal harvesting sizes and no-take areas in shallow habitats (<50 m).     

Habitat selection by the Mediterranean horseshoe bat, Rhinolophus euryale (Chiroptera: Rhinolophidae) in a rural area of southern Italy and implications for conservation

We studied habitat selection by Rhinolophus euryale in a rural area of southern Italy in 1998-2000 by radio-tracking. Two comparisons were carried out, one between habitat occurrence within individual home ranges and within the study area, the other between time spent in each foraging habitat and habitat occurrence within the home range. The first analysis showed that olive groves and conifer plantations were, respectively, the most and the least important habitats. The second analysis highlighted the importance of woodland for R. euryale, while urban sites, open areas and conifer plantations were avoided. We recommend that clearing of continuous, large areas of woodland for tree harvesting should be avoided. Conifers should not be used for reforestation. Urbanisation should be limited in the areas of greatest importance for the species, and linear landscape elements such as tree lines and hedgerows should be maintained.     

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.     

Decline in the distribution and abundance of flesh-footed shearwaters (Puffinus carneipes) on Lord Howe Island, Australia

The flesh-footed shearwater (Puffinus carneipes) is a migratory seabird that ranges widely across the Pacific and Indian Oceans. The principal breeding populations are in Australia and New Zealand. The only breeding site in eastern Australia is on Lord Howe Island. Despite it being afforded a high level of legislative protection, the population on Lord Howe Island has declined substantially during the last few decades. The total extent of nesting habitat in 2002 was 24.3 ha, a reduction of 13.4 ha (35.6%) since 1978. Loss of nesting habitat was associated with increased urbanisation, the adverse impact of which extended beyond the footprint of buildings and gardens. In 2002, overall burrow density was 0.123 per m² and the total number of burrows was estimated to be 29,853 ± 5867, a decline of about 19.0% since 1978. A substantial decline in burrow density was evident in the colony where loss of habitat to urbanisation had been greatest. In 2002, 58% of burrows were occupied by breeding birds, and the total population size was estimated to be 17,462 breeding pairs. Breeding success (the proportion of eggs that produced fledglings) was 50%, but was lowest in the most urbanised colony. To avert further declines in the population of flesh-footed shearwaters on Lord Howe Island major changes in land use practices, enforced through appropriate legislation, are needed, together with reductions in the level of seabird bycatch in fisheries operations and in the amount of plastics that litter the world’s oceans.     

Assessing quality of clearcut habitats for amphibians: Effects on abundances versus vital rates in the southern toad (Bufo terrestris)

Forest clearcutting is a form of habitat alteration that drastically alters the landscape and may contribute to declines in amphibian populations. Indeed, many studies have documented decreases in amphibian abundances and species richness in clearcuts. The development of effective conservation strategies to reduce the effects of timber harvesting has been hindered by lack of knowledge of the mechanisms underlying these changes in abundance. To better understand the potentially negative consequences of forest clearcutting, we used field enclosures in forested and clearcut habitats to examine changes in the survival and growth of juvenile southern toads (Bufo terrestris) over a two-month period. We also conducted a comparative monitoring study using drift fences and pitfall traps in forests and clearcuts to determine the effect of clearcutting on the abundance of juvenile southern toads. We found no significant effect of habitat on the number of juvenile southern toads captured in forests or clearcuts. In contrast, the average survival of toads in clearcut enclosures was significantly reduced compared to that of toads in forested enclosures (17 ± 5% versus 61 ± 3%). Toads surviving in clearcuts were also significantly smaller than those surviving in forested enclosures (27.9 ± 0.1 mm versus 30.3 ± 0.8 mm SVL). Our results highlight the difficulty in interpreting abundance patterns as a sole metric for habitat comparison. Because there is much interest in studying the effects of habitat alteration on amphibian populations, we recommend that future studies place more emphasis on determining changes in vital rates of populations following habitat alteration.     

Effects of fractions of coal-derived humic substances on seed germination and growth of seedlings (Lactuga sativa and Lycopersicum esculentum)

Summary Lettuce and tomato seeds were treated in Petri dishes with a humic acid derived from an oxidized coal and with fractions of the same humic acid obtained by ultrafiltration through membranes of known molecular cutoff and by extracting with buffers set at pH 4 and pH 5. The unfractionated humic acid was applied at 40, 100, 1000, and 5000 mg l^-1 whereas the humic fractions were applied at 40, 100, and 200 mg l^-1. Germination parameters such as the number of total germinated seeds, the velocity of seed germination, the fresh weight and dry weight of total seedlings were measured and related to the chemical and physicochemical properties of the humic material. No increase in the germination percentage or the germination rate was observed for either lettuce or tomato seeds. The fresh weight of total seedlings and per seedling increased in treatments with unfractionated humic acid with increasing concentrations for both lettuce and tomato plants without showing signs of growth inhibition up to 5000 mg l^-1. This was attributed to cell elongation and more efficient water uptake. For the lettuce, the fresh weight both of total seedlings and per seedling was enhanced by treating the seeds with fractions of low molecular weight and high content of acidic functions, whereas the dry weight both of total seedlings and per seedling did not change with the humic fraction used. For the tomato seeds in contrast, the dry weight both of total seedlings and per seedling was increased by the use of unfractionated humic acid and by some of the humic fractions. An uptake of humic material by growing tomato seedlings was inferred.     

Response of Pinus leucodermis to climate and anthropogenic activity in the National Park of Pollino (Basilicata, Southern Italy)

Pinus leucodermis (=P. heldreichii var. leucodermis) is widespread in the Balkan Peninsula and is present as a post-glacial relict in Southern Italy. The oldest Italian populations of this species are located at high elevation in the National Park of Pollino, where grazing and logging had endangered their survival, especially during the 20th century. In 1993 the National Park was founded and anthropogenic activities were restricted. To understand the response of P. leucodermis at the upper tree-line to climatic and anthropogenic activity variations, we developed a tree-ring width chronology (1464-2003). For the period 1804-2003 separate chronologies for the earlywood and latewood were built, and resin duct density was assessed on total ring, earlywood and latewood. Age structure of saplings was also determined. After 1950 a steep decline in tree-ring width was followed by a recovery since 1981. During the 20th century radial growth response to climate was not strong and not stable. In the period 1953-2000 P. leucodermis radial growth seemed to take advantage of high temperatures and low precipitation. Resin duct density chronologies were not a reliable dendroecological variable, but they documented a metabolic trade-off between growth and differentiation processes. The gap in the age structure between long-lived trees (over 200 years old) and saplings around 40 years old, which mainly grow in protected microsites between rocks, could indicate a negative influence of grazing and related human activities. We suggest that the protection strategies introduced by the National Park could play a positive role in the recruitment of new saplings and in the ring growth recovery of old trees of P. leucodermis.     

Correlates of abundance and breeding success in the globally threatened Hinde's babbler (Turdoides hindei) and its congener, northern pied babbler (T. hypoleucus)

We investigated the relationship between habitat quality, abundance, group size and breeding success in the threatened Kenyan endemic Hinde's babbler (Turdoides hindei; Family Timaliidae), a co-operative breeder mainly associated with riverine thickets in cultivated areas. At two intensively cultivated sites, significantly more Hinde's babbler groups occurred in areas retaining at least 3% thicket cover, while breeding outcome improved where cover exceeded 9%. Despite previous concerns over low breeding success, the percentage of young birds present (17%, n=424 birds aged) was similar to that of a sympatric congener, the northern pied babbler (T. hypoleucus) (12%, n=162), and comparable with that of two other African congeners. Although breeding outcome was positively correlated with adult group size, there was no evidence that larger groups monopolised more favourable habitat or defended larger territories. Group density showed a positive, non-linear relationship with adjacent cover, levelling out where this exceeded 15-20%. Our findings suggest that even a modest increase in thicket cover may significantly raise the density and productivity of Hinde's babblers at these sites.     

Forest fragmentation and the distribution, abundance and conservation of the Tana river red colobus (Procolobus rufomitratus)

Evidence suggests that habitat heterogeneity, disturbance, disease, predation and food resources influence primate population abundance. However, few studies have focused on what habitat factors determine the probability that a primate species will occur in a habitat fragment. We analysed forest habitat and colobus population attributes to determine factors that influenced occurrence and abundance of the critically endangered Tana River red colobus. The probability of colobus inhabiting forests was positively related to the relative amount of habitat edge and canopy tree species composition. Most of the variance in the density of colobus monkeys was explained by basal area of food trees (per ha), basal area per food tree, density of food trees, and basal area per tree for all trees. We conclude that effective conservation of primates in fragmented habitats may require strategies that consider factors that influence both the occurrence of a species and its relative abundance.