Comparative use of three methods for estimating the population size of a transferred island endemic: the endangered Seychelles White-eye Zosterops modestus

SummaryThe Raso Lark Alauda razae is a single island endemic confined to the island of Raso in the Cape Verde islands. It has been studied via short (11–20 day), similarly-timed visits every year from 2001 to 2017. These November/December visits have occurred towards the end of the main rainy period (August–October) in the Cape Verdes. Average clutch size ranged from zero (no nests found) to 3.57 in different years and was strongly correlated with rainfall in the three months preceding the year’s visit, but not with population size, which varied 25-fold during the study period. Since the nomadic pursuit of rain is not an option for the Raso Lark, the species adjusts clutch size according to conditions prevailing on Raso.

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Assessing the status of a threatened island endemic, Ctenosaura oedirhina, on Roatán, Honduras

Wildlife Research ◽

10.1071/wr18195 ◽

2020 ◽

Vol 47 (2) ◽

pp. 137

Author(s):

A. B. C. Goode ◽

S. A. Pasachnik ◽

T. L. Maple

Keyword(s):

Population Size ◽

Distance Sampling ◽

Adult Mortality ◽

Isolated Populations ◽

Cultural Traditions ◽

Island Endemic ◽

Wild Fauna ◽

The Status ◽

In The Wild ◽

Study Sites

Abstract Context Organisms living in small, isolated populations with very restricted ranges are at high risk of extirpation due to various direct and indirect forces than mainland populations. Roatán spiny-tailed iguanas (Ctenosaura oedirhina) are endemic to the 146-km2 island of Roatán, Honduras. Harvesting for consumption, fragmentation of habitat and predation by domestic animals threaten the existence of this lizard. This species is federally protected in Honduras; however, enforcement is rare. These iguanas are also listed as Endangered by the International Union for Conservation of Nature (IUCN) and are on Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). This species is geographically and genetically isolated into small subpopulations that are declining in density. Aims To estimate the population size of Roatán spiny-tailed iguanas (Ctenosaura oedirhina) on the island of Roatán, Honduras. Methods Distance sampling surveys have been used to monitor this species since 2012, and have been used to determine population density at five study sites. Estimates of density at those sites and across the island were used to calculate the population size of this species. Key results The present study elucidates that the high-density populations remaining are declining. The current population size is estimated to be 3759 (95% CI=1406–12616) individuals within the study sites, with 730 additional iguanas potentially outside of the study sites. Conclusions If the current level of decline continues, this species may become extirpated from some locations on Roatán, and go extinct in the wild. Although Honduras does have laws protecting this species and other wildlife, enforcement must be enhanced. Implications Lack of enforced protection for this species allows poaching for consumption to continue, which has been shown to alter its distribution and cause increased adult mortality. Local customs value the consumption of this species, creating a delicate management situation. Recommendations include strategies that mitigate the threat posed by consumption and increase enforcement of the current laws, while acknowledging cultural traditions.

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Low diversity, little genetic structure but no inbreeding in a high density island endemic pit-viper Gloydius shedaoensis

Current Zoology ◽

10.1093/cz/zoab084 ◽

2021 ◽

Author(s):

Guannan Wen ◽

Long Jin ◽

Yayong Wu ◽

Xiaoping Wang ◽

Jinzhong Fu ◽

...

Keyword(s):

Genetic Diversity ◽

Genetic Structure ◽

Population Size ◽

Demographic History ◽

Iucn Red List ◽

Conservation Priorities ◽

Important Species ◽

Island Endemic ◽

Island Species ◽

Low Genetic Diversity

Abstract Islands species and their ecosystems play an important role in global biodiversity preservation, and many vulnerable island species are conservation priorities. Although insular habitat likely facilitates the species diversification process, it may also aggravate the fragility of these species with high risk of inbreeding. The Shedao pit-viper Gloydius shedaoensis is an island endemic species with an extremely high population density, which has been categorized as vulnerable in the IUCN Red List. We collected 13,148 SNP from across its genome and examined its genetic diversity and demographic history. The Shedao pit-viper has a low genetic diversity but shows no sign of inbreeding. Furthermore, population genetic structure analysis, including the NJ tree, PCoA, clustering, and spatial autocorrelation, revealed a general lack of spatial structure. Only the IBD residues suggested a weak patchiness. Overall, the population is nearly panmictic and gene flow is evenly distributed across the island. The large number of individuals, small size of the island, and the lack of population structure likely all contribute to the lack of inbreeding in this species. We also detected signs of male-biased dispersal, which likely is another inbreeding avoidance strategy. Historical demographic analysis suggested that the historical population size and distribution of the species are much larger than their current ones. The multiple transgressive-regressive events since the Late Pleistocene are likely the main cause of the population size changes. Taken together, our results provide a basic scientific foundation for the conservation of this interesting and important species.

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Estimated population size of the Island Scrub-Jay Aphelocoma insularis

Bird Conservation International ◽

10.1017/s0959270900000137 ◽

2000 ◽

Vol 10 (2) ◽

pp. 137-148 ◽

Cited By ~ 8

Author(s):

Rodd Kelsey ◽

Charles T. Collins

Keyword(s):

Population Size ◽

Total Population ◽

Breeding Population ◽

Population Viability ◽

Territory Size ◽

Population Estimate ◽

Santa Cruz Island ◽

Island Endemic ◽

Exotic Tree ◽

Aphelocoma Insularis

As an island endemic, the Island Scrub-Jay's Aphelocoma insularis population status and conservation are of concern. In addition, because the Island Scrub-Jay is easily observed, it is an ideal candidate for monitoring the effects of management efforts on Santa Cruz Island, California. We used estimates of territory size in several different habitats occupied by the Island Scrub-Jay and the total area of these habitats on the island to develop an empirical estimate of the population size for this species. Our most conservative, and we feel most realistic, estimate for the Island Scrub-Jay breeding population is 7,000 individuals and for the non-breeding population 5,500 individuals, yielding a total population estimate of 12,500. Even though conservative, this estimate is larger than earlier estimates of 4,000 to 6,000 individuals. Even so, our data suggest no reason exists for immediate concern regarding the population viability of the Island Scrub-Jay and they provide a baseline for future estimates and comparisons. Most importantly, this population estimate can be used to monitor the influence on the Island Scrub-Jay of future island management efforts, especially regarding exotic tree species and feral pigs.

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Hierarchical distance-sampling models to estimate population size and habitat-specific abundance of an island endemic

Ecological Applications ◽

10.1890/11-1400.1 ◽

2012 ◽

Vol 22 (7) ◽

pp. 1997-2006 ◽

Cited By ~ 72

Author(s):

T. Scott Sillett ◽

Richard B. Chandler ◽

J. Andrew Royle ◽

Marc Kéry ◽

Scott A. Morrison

Keyword(s):

Population Size ◽

Distance Sampling ◽

Island Endemic ◽

Estimate Population Size

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European Colonization, Not Polynesian Arrival, Impacted Population Size and Genetic Diversity in the Critically Endangered New Zealand Kākāpō

Journal of Heredity ◽

10.1093/jhered/esw065 ◽

2016 ◽

Vol 107 (7) ◽

pp. 593-602 ◽

Cited By ~ 9

Author(s):

Laura M. Bergner ◽

Nicolas Dussex ◽

Ian G. Jamieson ◽

Bruce C. Robertson

Keyword(s):

Genetic Diversity ◽

New Zealand ◽

Population Size ◽

Demographic History ◽

Critically Endangered ◽

Museum Specimens ◽

Human Settlement ◽

Island Endemic ◽

Population Size Estimates ◽

European Colonization

Abstract Island endemic species are often vulnerable to decline and extinction following human settlement, and the genetic study of historical museum specimens can be useful in understanding these processes. The kākāpō (Strigops habroptilus) is a critically endangered New Zealand parrot that was formerly widespread and abundant. It is well established that both Polynesian and European colonization of New Zealand impacted the native avifauna, but the timeframe and severity of impacts have differed depending on species. Here, we investigated the relative importance of the 2 waves of human settlement on kākāpō decline, using microsatellites and mitochondrial DNA (mtDNA) to characterize recent kākāpō genetic and demographic history. We analyzed samples from 49 contemporary individuals and 54 museum specimens dating from 1884 to 1985. Genetic diversity decreased significantly between historical and contemporary kākāpō, with a decline in mean number of microsatellite alleles from 6.15 to 3.08 and in number of mtDNA haplotypes from 17 to 3. Modeling of demographic history indicated a recent population bottleneck linked to the period of European colonization (approximately 5 generations ago) but did not support a major decline linked to Polynesian settlement. Effective population size estimates were also larger for historical than contemporary kākāpō. Our findings inform contemporary kākāpō management by indicating the timeframe and possible cause of the bottleneck, which has implications for the management of extant genetic diversity. We demonstrate the broader utility of a historical perspective in understanding causes of decline and managing extinction risk in contemporary endangered species.

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Reduction of spermatogonia and testosterone in rat testes flown on space lab-3

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100142864 ◽

1986 ◽

Vol 44 ◽

pp. 248-249

Author(s):

Delbert E. Philpott ◽

W. Sapp ◽

C. Williams ◽

T. Fast ◽

J. Stevenson ◽

...

Keyword(s):

Social Interaction ◽

Social Status ◽

Population Size ◽

Physiological Response ◽

Social Rank ◽

Reproductive Function ◽

Testicular Development ◽

Organ Weights ◽

Reproductive Maturation ◽

Metabolic Activities

Space Lab 3 (SL-3) was flown on Shuttle Challenger providing an opportunity to measure the effect of spaceflight on rat testes. Cannon developed the idea that organisms react to unfavorable conditions with highly integrated metabolic activities. Selye summarized the manifestations of physiological response to nonspecific stress and he pointed out that atrophy of the gonads always occurred. Many papers have been published showing the effects of social interaction, crowding, peck order and confinement. Flickinger showed delayed testicular development in subordinate roosters influenced by group numbers, social rank and social status. Christian reported increasing population size in mice resulted in adrenal hypertrophy, inhibition of reproductive maturation and loss of reproductive function in adults. Sex organ weights also declined. Two male dogs were flown on Cosmos 110 for 22 days. Fedorova reported an increase of 30 to 70% atypical spermatozoa consisting of tail curling and/or the absence of a tail.

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