From genetic diversity and structure to conservation: Genetic signature of recent population declines in three mouse lemur species (Microcebus spp.)

The exceptional biodiversity of Madagascar is threatened by anthropogenic landscape changes that took place during the 2000 years of human colonization. This study focuses on the influence of geographic distance and forest fragmentation on genetic diversity and population differentiation of three rare, nocturnal, arboreal lemur species in northwestern Madagascar. Historic declines in population sizes as a consequence of forest fragmentation are quantified and dated. Eighteen sites were visited, and a total of 205 Microcebus ravelobensis, 45 M. bongolavensis and 78 M. danfossi were genotyped with eight microsatellite loci. Genetic differentiation among the sites, as measured by F_ST, ranged from 0.01 to 0.19. These values were significant in almost all cases and indicated genetic structure in the samples. Isolation-by-distance was detected in one species and a STRUCTURE analysis indicated that fragmentation further promoted genetic differentiation. Bayesian methods revealed that populations from all three species underwent a major demographic collapse of around two orders of magnitude. This decrease probably began after the arrival of humans, most likely within the last 500 years. This result suggests that anthropogenic changes may have been limited during the first 1500 years of human colonization in all three ranges. Two of the study species (M. danfossi, M. bongolavensis) lack effectively protected areas in their ranges. Consequently, quick conservation actions are now needed in order to secure the remaining genetic diversity of these species.     

Conservation and management of Britain's reptiles based on their ecological and behavioural requirements: A progress report

Britain's native reptile fauna consists of three lizard species and three snake species, some of which may be unique physiological races (evidence is so far based only on their Critical Minimum Temperatures). Three species (Anguis fragilis, Lacerta vivipara, Vipera berus) are widely distributed although the populations are fragmented. The other three (Coronella austriaca, Lacerta agilis, Natrix natrix) are more or less limited in distribution to southern England (although N. natrix does reach Latitude 56°N) and most of the populations are small, scattered and geographically isolated from each other. Pressures such as land development, collecting and habitat destruction by fire are great. The snake Coronella austriaca and the lizard Lacerta agilis are now rare and several colonies and/or habitats of these two species are destroyed each year. As the survival of Britain's rarer reptiles may depend on well managed nature reserves and on the relocation of endangered colonies it is imperative that much more basic herpetological research be completed during the next few years. Fundamental eco-physiological requirements (e.g. food, heat, water) and behavioural requirements (e.g. space) of these animals are being examined in order to maintain or develop optimum habitats on nature reserves and in the hope of establishing viable reptile colonies. One example of this procedure is discussed with particular reference to the construction of an island habitat for Lacerta agilis, and suggestions for future management are outlined.     

The recent status of Monachus monachus, the Mediterranean monk seal

Mediterranean monk seals Monachus monachus (Hermann 1779) still live widely in their primaeval range around the Mediterranean and adjacent northeast Atlantic seas, but are now confined chiefly to remote cliffbound coasts and islets. Greatest numbers occur in the eastern Aegean sea. Total numbers are probably between 500 and 1000 with the population still declining. Neonates measure about 0·8 m length and weigh about 20 kg, while adults reach extreme sizes of 3m and 400 kg. The wide food spectrum of fish and cephalopods, probably reaching 5% of body weight per day as an optimum intake for adults, produces competition with fishermen. Seals damage nets and are shot, and are also caught inadvertently in various types of nets. Births extend from May to November with a peak in September. Human disturbance of reproductive sites at all seasons is believed to be seriously reducing the reproductive rate of monk seals. Efficient reproduction probably requires beaches as well as the caves mostly used at present. Individual travel can be several hundred kilometres and widespread similarity of colour patterns suggests that gene flow has not been interrupted in the past. A network of reserves is needed in existing and past habitat, which could be of value also to rare cliff-nesting sea birds. These core reserves should be totally free of human disturbance, but buffer zones are envisaged surrounding them, which could be used for viewing the animals.     

Reproductive constraints for the long-term persistence of fragmented Acacia dealbata (Mimosaceae) populations in southeast Australia

Fragmented and degraded vegetation characterises agricultural landscapes across southern Australian. Remnant vegetation within these regions performs a number of vital ecological and hydrological roles, but little is known about whether or how fragmentation is affecting the long-term persistence of these critical landscape elements. Acacias are a significant component of many remnant vegetation communities across Australia, forming numerous integral faunal and floral relationships. Here, reproductive output of 11 fragmented Acacia dealbata (Mimosaceae) populations from across the southern tablelands of New South Wales was assessed over 2 years to identify reproductive constraints associated with increasing vegetation fragmentation. Fertilization success is the major reproductive constraint, particularly in small populations, and probably reflects a self-incompatible reproductive strategy. During 2002 larger and more dense populations produced more legumes (p = 0.014 and <0.001, respectively) while in 2003 these two variables were associated with increased fertilization success (p = 0.004 and 0.017, respectively). There was also some suggestion that populations with fewer exotic species also experienced increased fertilization success (p = 0.055). Assessment of plant performance within populations suggests that consistent reproductive output of particular individuals within small populations may limit reproductive compatibility within these populations over time. The long-term persistence of many small A. dealbata populations may be jeopardised by low seed set, and limited recruitment and aging stands. Immediate steps are now required to ensure that these populations continue contributing to landscape function by augmenting populations, improving connectivity, and allowing disturbance events that will stimulate recruitment.     

Atlantic salmon resources in the Northeastern United States and the potential effects of acidification from atmospheric deposition

The Atlantic salmon (Salmo salar) was formerly abundant in northeast coastal rivers in the United States from the Canadian border to the Connecticut River, and possibly as far south as the Delaware River. It was eliminated from most of its former range by a combination of overfishing, construction of dams impassable to migrating fish, and municipal and industrial pollution. Reproducing populations are now limited to a few rivers in Maine, but attempts are under way to reintroduce the species to some rivers where populations formerly existed. Most of the native Atlantic salmon rivers are low in acid neutralizing capacity and receive acidic precipitation. The third order streams are not now acidic; however, in some first and second order streams in Maine, pH episodically declines to 4.7 and Al increases to 350 μg g^?1. These conditions could be toxic to sensitive early life history stages of Atlantic salmon. Comparison of chemical conditions in two Maine rivers in 1980–1982 with those in 1969–1970 indicated that the streams have not become more acidic during this interval. Data on the sport catch of Atlantic salmon indicated that populations have generally remained stable or recently increased in the Maine rivers having naturally reproducing populations. The recent increase probably resulted from introductions of hatchery smolts to supplement natural reproduction, and the occurrence of strong year classes in 1978 and 1980. The population in one stream has declined significantly in recent years, but the cause of the decline is probably not related to acidic precipitation. Atlantic salmon resources in the U.S. have apparently not been adversely affected by atmospheric deposition at the present time.     

Long-term trends in the demography of the Allen Cays Rock Iguana (Cyclura cychlura inornata): Human disturbance and density-dependent effects

Allen Cays Rock Iguanas (Cyclura cychlura inornata) are native to two small islets (Leaf and U Cay) in the north-central Bahamas. These populations were nearly extirpated in the early 1900s because of heavy hunting pressure (for food), but increased to a total of ca. 150 lizards in 1970, and now number over 500 (not including juveniles). Over the past several decades poaching has declined, but tourist visitation (including nearly daily supplemental feeding of iguanas) has increased. To examine human impacts on the demography of these iguanas, survival, population growth rates, and population sizes for subadult and adult (>25 cm snout-vent length) males and females on the two cays were estimated based on mark-recapture data collected over a 25-year period (1980-2004). As predicted, annual survival probability was higher on U Cay (with less human visitation) than on Leaf Cay, was higher in females than in males (which are bolder), and exhibited a declining trend. Both populations more than doubled during this study, but population growth rates declined to near zero in recent years. These data reflect the importance of human impacts, but also suggest that the populations may be nearing carrying capacity. The rapid population growth observed on these cays, and that seen for several other translocated iguana populations, suggest that if unnatural causes of mortality are reduced or eliminated, island populations of iguanas are capable of rapid recovery. The inexpensive establishment of assurance colonies on undisturbed “islands” should be considered for any comprehensive management plan for endangered species of iguanas.     

Phocine distemper virus in the North and European Seas - Data and models, nature and nurture

Two outbreaks of phocine distemper have severely affected harbour seal (Phoca vitulina) populations in European and UK waters. The first occurred in 1988 when the causative virus was identified as a new member of the genus morbillivirus. The second outbreak in 2002 was first detected on the same Danish Island of Anholt and involved similar populations and geographical locations. However, despite the obvious similarities between the epidemics, differences in viral transmission and case mortality were found. Harbour seals are highly susceptible to infection while sympatric grey seals (Halichoerus grypus) are resistant but could be important asymptomatic carriers of the disease. Arctic phocid seals remain the most likely source of the virus and grey seals could be the link between these primary hosts and the harbour seal populations further south. Future epidemiological models should therefore consider including multiple host species. The future conservation and management of harbour seal populations vulnerable to PDV relies on the ability to accurately predict the long-term impact on population abundance and distribution. Although knowledge about the behaviour and pathogenesis of the virus has increased substantially and data on host movements and contact rates are accumulating, studies into the determinants of the host range have lagged behind. The development of more realistic epidemiological models should be combined with studies into the factors controlling species and individual susceptibility. Assessing the risk of infection to endangered but currently unexposed potential host species (such as the Hawaiian monk seal, Monachus schauinslandi) is essential for guiding potential conservation management options, such as vaccination     

The status of the health fritillary butterfly Mellicta athalia Rott. in Britain

An extensive survey was made of known and potential sites of the heath fritillary butterfly Melllicta athalia Rott. in Great Britain in 1980. The size of every colony found was measured and information obtained on its habitat preferences and larval foodplants. Details of all the sites that still support this butterfly are summarised and its habitat requirements are assessed.The survey confirmed that the heath fritillary is probably the most endangered resident butterfly in Britain. It has declined severely in recent years and is now restricted to five sites in SW England and to three woodland blocks in E Kent. Thirty-one colonies were discovered (6 in the SW, 25 in Kent), but 24 of these contained fewer than 200 adults on the peak day. Moreover, several occurred close to larger populations and may only be offshoots that would not be viable on their own.The heath fritillary has different habitat requirements in SW England and Kent, although in both regions it needs sunny sheltered woodland that is at an early stage of succession or regeneration. Such habitat is ephemeral and must be generated continuously within fairly small areas if it is to be utilised, for the butterfly rarely flies long distances. Nearly all documented extinctions have been caused by a loss of suitable habitat from the locality, for this is only occasionally created by most modern forms of silviculture. In Kent, the heath fritillary survives mainly in the ever-decreasing areas where traditional coppicing has continued, but the future of this practice is now in doubt. Few colonies survive in SW England, although some are now being managed specifically to safeguard the butterfly.     

Population genetic structure of in situ wild Sorghum bicolor in its Ethiopian center of origin based on SSR markers

In situ population studies of wild relatives of crops are crucial for the conservation of plant genetic resources, especially in regions with high genetic diversity and a risk of local extinction. Ethiopia is the center of origin for sorghum, yet little is known about the genetic structure of extant wild populations. Using 9 Simple Sequence Repeat loci, we characterized 19 wild populations from five regions, 8 local cultivar populations from three regions, and 10 wild sorghum accessions from several African countries. To our knowledge, this is the most comprehensive study to date of in situ wild sorghum populations in Africa. Genetic diversity corrected for sample size was significantly greater in the wild populations in situ than in local cultivars or the accessions. Approximately 41 % of the genetic variation in the wild plants was partitioned among populations, indicating a high degree of differentiation and potential value for germplasm conservation, and the average number of migrants (N_m) per generation was 0.43. Cluster analyses showed that some wild populations were grouped by geographic region, whereas others were not, presumably due to long-distance seed movement. Four wild populations from disjunct regions formed a unique cluster with an Ethiopian accession of subsp. drummondii and probably represent a weedy race. STRUCTURE and other analyses detected evidence for crop-wild hybridization, consistent with previous molecular marker studies in Kenya, Mali, and Cameroon. In summary, in situ wild sorghum populations in Ethiopia harbor substantial genetic diversity and differentiation, despite their close proximity to conspecific cultivars in this crop/wild/weedy complex.     

International efforts to save the tiger from extinction

The Tiger (Panthera (Felis) tigris) has suffered a catastrophic decline in numbers in all countries within its range, so that, today, there are probably no more than 5,000 animals of the eight races remaining in the wild. Although, in certain countries, the Tiger is given protection, in others it is still under heavy persecution. Surviving populations are now too scattered to maintain a viable genetic interchange. The chief cause of the decline has been the massive destruction of forests in Asia, but unrestricted hunting and poisoning and the demand for skins by the fur trade have also been important factors. Strenuous international efforts are now being made to create fourteen special reserves in order to save the Indian Tiger race, of which about 2,350 individuals remain.     

Status and conservation of the grey seal, Halichœrus grypus, in France

We investigated the status of the grey seal in the Molène archipelago, western Brittany, where a Marine National Park is planned. We combined regular censuses, photo-identification and satellite telemetry to investigate trends in grey seal abundance, site fidelity, individual movements and haulout site use. Individual movements and seasonal variations in abundance suggest that the seals used the Molène archipelago alternatively with other haulout sites of the South-west British Isles during their annual cycle. Nine out of 16 seals fitted with Satellite Relay Data Loggers (SRDLs) moved to the Isles of Scilly, English Cornwall, Wales or the Channel islands. On average the seals spent 85% of their time Near Haulout, 56.8% of which in the Molène archipelago. Overall the seals spent 66% of their tracking time within the boundaries of the Marine National Park. From 1997 to 2000 in the Molène archipelago, we observed a peak in number during the moulting season (mean = 49.8 seals) and a lower abundance during the breeding season (mean = 38.3 seals). The sex ratio was strongly skewed towards males during the moult (between 3.1 and 5.3-1), and was close to 1:1 during the summer. Inter-annual site fidelity outside the breeding season was very high, varying from 70% to 95% of identified seals, suggesting that the observed movements constitute rotations rather than random dispersion. From 1991/1994 to 1997/2000, the mean number of seals counted at haulout sites increased by 7%, close to the rates of increase observed in the core population of the British Isles at the same period. The Marine National Park may be too restricted for the overall conservation of the population but management plans should be aimed at preserving the characteristics of the habitat for the grey seal.     

Growth and recruitment of Acanthaster planci (L.) on the great barrier reef

Size classes can be discerned in field size frequency data for Acanthaster planci which may be interpreted as age classes. This interpretation enables a possible field growth curve to be derived, which is consistent with measured growth data from the laboratory (Yamaguchi, 1974) and from field experiments by Pearson & Endean (1969).The aging of size classes enables measured size frequency data for A. planci on the Great Barrier Reef between 1966 and 1976 to be discussed as a recruitment history of the starfish.A. planci populations on all reefs for which size frequency data are available appear to have increased as a result of larval recruitment, rather than through adult migration. There appear to have been three main waves of recruitment, each affecting a section of reef spanning one to two degrees of latitude. The parental stock of the originally observed large populations of A. planci on the Great Barrier Reef was probably located north of 16° 30′ S.     

Life expectancy of monk seal colonies in Greece

A calculation of the life expectancy of the few remaining colonies and individuals of the Mediterranean monk seal Monachus monachus in Greek waters has been made. This is based on the 1977 census of the seal population by Vamvakas et al. (1978) with corrections based on observations by the author, and application of the rate of decline of all populations of seals by J. Boulva (1978). The results indicate that no seals will be left in Greece by the year 2000, and many colonies will have ceased to exist by 1990. The colonies with the greatest life expectancy are located in the Ionian sea, the Sporades, and in islands around Crete.The discouraging results of the calculations emphasize the urgency of immediate action to preserve the few remaining seals in Greece.     

Arctic marine mammals as integrators and indicators of mercury in the Arctic

Mercury concentrations were determined in liver, kidney and muscle of belugas, narwhal, whitebeaked dolphins, pilot whales, ringed seals, harp seals and walrus. Tissue collections and analyses were performed largely over the past 10 years. Sampling sites ranged across the Canadian Arctic from the Mackenzie Delta and Banks Island in the west, Grise Fjord in the north, the Atlantic coast in the east and south. High Hg levels in the liver of ringed seals from the western Arctic, collected in 1987 and 1988 were similar to previously-reported values for ringed seals collected in 1973 and 1972 from the same area. Comparison among different marine mammal species showed substantial inherent differences in Hg levels among different species. White-beaked dolphins and walrus had much less Hg than pilot whales. A comparison of Hg levels in ringed seals from locations across the Arctic and Hudson Bay showed that Hg was generally higher in ringed seals from the western than the eastern Arctic, indicating a possible influence of the different geological settings in the eastern and western Arctic. The effect of age was considered in these comparisons. A similar, but less pronounced effect was noted for belugas, with some possible anthropogenic influence on animals in Hudson Bay. The spatial trend in Hg levels in animals appeared to be largely present-day background concentration reflecting geological differences between the eastern and western Arctic. Higher Hg concentration were present in surficial sediments and coastal waters in the western Arctic than the eastern Arctic in accord with the Hg trend observed in seals and belugas.     

The distribution of disturbance-dependent rare plants in a coastal Massachusetts sandplain: Implications for conservation and management

Rare plants in coastal New England sandplains are often restricted to anthropogenically disturbed sites including plowed and mowed firelanes at the Manuel F. Correllus State Forest on Martha’s Vineyard. Little is known about pre-colonial rare plant habitat or how modern management impacts these species. To understand the factors influencing rare plant distribution, we examined the influence of vegetation structure, species composition, environmental characteristics and disturbance history on rare plant populations and potential natural habitat in the 2100-ha Forest. We sampled >100, 100 m² plots - in firelanes and forested/shrubland areas - and conducted extensive searches for rare plants.Linum intercursum and Scleria pauciflora var. caroliniana were frequent in firelanes including in recently plowed areas, whereas Nabalus serpentarius, Sisyrinchium fuscatum, and Aristida purpurascens generally occurred in isolated, locally-abundant patches in firelanes not plowed for many decades. The former group may be characterized by an ability to rapidly establish following disturbances while the latter may take longer to establish and develop large populations. In some respects, rare plants were associated with environmental conditions reflecting the disturbance histories of sites they occupied (e.g., L. intercursum with lower duff depth and N. serpentarius with greater litter cover/depth).In forests and shrublands undisturbed for decades, rare plants only occurred on well-worn paths. Although scrub oak stands supported conditions more similar to those found in firelanes than other native vegetation types, disturbances - far more severe than those in forests/shrublands of the past century - are probably required to create suitable rare plant habitat in sandplain forests and shrublands.     

The ecology of the mediterranean tortoise Testudo hermanni in northern Greece (the effects of a catastrophe on population structure and density)

Two large, dense and viable populations of Testudo hermanni inhabiting adjacent sites in northern Greece were studied over three years. One site experienced severe habitat destruction by fire during the course of the study, and the other may either have been seriously disturbed in a single event several years previously, or is suffering from a continual low level of disturbance. In the stable situation average population density was estimated as 45 tortoises ha ⁻¹ and in parts may have reached 100 ha⁻¹ The adult sex ratio was biased 2:1 in favour of males, due to higher female mortality. Most animals were sedentary, but there were some seasonal movements between vegetation types for feeding. The immediate effect of the fire was an estimated 40% population reduction, with juveniles being most severely affected. Subsequently the growth rate of immature animals rose sharply. This study demonstrates the relative resistance of tortoise populations to a sudden and temporary catastrophe, and their high potential for recovery if left undisturbed.     

The first occurrence of the brown alga sargassum muticum (yendo) fensholt in the channel islands

An ‘unusual’ alga reported by the Jersey Department of Agriculture was positively identified as Sargassum muticum (Yendo) Fensholt (Phaeophyta, Fucales).Limited field investigations revealed the alga's presence at three sites in Jersey— St Helier, L'Etacq and Le Hocq. The largest population of the two at St Helier occupied a tidal man-made swimming pool and, due to favourable local conditions, was reproductively in advance of English south coast populations. Sargassum was easily the dominant algal species in the pool. Other S. muticum populations in Jersey were at similar stages of reproductive development to English south coast populations. All occupied sites which never completely drained.Sargassum was probably introduced to St Helier by shipping. The other populations may have arisen from fertile drift plants from St Helier or alternatively from one of the large French coast populations. The Channel Islands provide many sites suitable for Sargassum growth and further spread and consolidation of the alga can be expected.     

Assessing limitations on population growth in two critically endangered Acacia taxa

Flowering phenology, soil seedbank and the impact of fire, weeds and grazing were investigated in two rare Acacia taxa restricted to the agricultural district north of Perth Western Australia. Acacia aprica is known from six extant populations and one extinct population. Five of the extant populations are restricted to linear road reserves with the sixth population located in a small native vegetation remnant. Acacia cochlocarpa ssp. cochlocarpa is known from a single population also situated on a road verge. Size class structure, levels of canopy death and an absence of juveniles indicated that all populations are in decline. Flowering intensity and success varied between populations and years in A. aprica and between years in A. cochlocarpa ssp. cochlocarpa. Seed bank analysis indicated that seeds were patchily distributed while experimental fires demonstrated that such events could break seed dormancy and promote germination. Both taxa have similar germination physiologies and showed increased germination after seeds were exposed to heat. Following emergence, however, competition with annual weeds had a negative impact on seedling growth and survival in both taxa. While vertebrate grazing had some influence, weeds were the major inhibitory influence on recruitment. Reduced fire frequencies since fragmentation may be responsible for population decline in both taxa but other site specific factors such as weeds and grazing may affect the establishment of seedlings following fire.     

The decline of boody (Sulidae) populations in the western Indian Ocean

Booby (Sulidae) populations in the western Indian Ocean have declined markedly in the last hundred years. All species have lost at least half of their colonies while those which survive are reduced in size, and S. abbotti is extinct in this region. Most of the population changes are attributable to man's activities, for example, the exploitation of boobies for food, the introduction of predators and the destruction of breeding areas, especially during guano extraction. Tourism may now pose an additional threat and measures are required to monitor all existing colonies and protect at least some of them.     

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.