Habitat fragmentation increases genetic distance between fruit bat subpopulations

Abstract
Livingstone's fruit bat (Pteropus livingstonii) is among the most threatened bats worldwide. As the species is an important pollinator and seed disperser of Comoros plants with a crucial role in forest regeneration, it is critical to understand how human-induced habitat disturbance impacts genetic structure at fine spatial scales in order to define conservation strategies. In this study, we assessed the level of genetic structure between eight colonies of the species and found that this was strong genetic structures between roosts that can be explained by isolation due both to distance and habitat fragmentation. Mitigation measures should aim to restore population connectivity.

Résumé
La chauve-souris frugivore de Livingstone (Pteropus livingstonii) est l’une des chauvessouris les plus menacées au monde. L’espèce étant un important pollinisateur et disperseur de graines des plantes des Comores et jouant un rôle crucial dans la régénération des forêts, la compréhension de l’impact des perturbations de l’habitat induites par l’homme sur la structure génétique à des échelles spatiales fines est essentielle pour définir des stratégies de conservation. Dans cette étude, le niveau de structure génétique de huit colonies de l’espèce a été évalué et nous avons constaté qu’il existait une forte structure génétique entre les perchoirs, pouvant s’expliquer par l’isolement dû à la fois à la distance et à la fragmentation de l’habitat. Les mesuresvisant à atténuer les effets de la pollution devraient avoir pour objectif de rétablir la connectivité entre les populations.

Habitat Suitability and Population Size Estimates for the Mongoose Lemurs (Eulemur mongoz) of Madagascar and the Comoro Islands, and Implications for Their Conservation

Mohamed Thani Ibouroi, Said Ali Ousseni Dhurham and Clément Rabarivola

Abstract

Tropical forests face an alarming rate of loss driven by anthropogenic pressures, exposing forest-dwelling species such as primates to extinction risks. Assessing population density and habitat selection by these species can provide insights into how they respond to habitat fragmentation and inform efective conservation. We investigated the population density and size of the mongoose lemur (Eulemur mongoz), a Critically Endangered primate species from Madagascar and the Comoro Islands using (1) conventional distance sampling, and (2) density surface modeling. We also used species distribution modeling to assess the habitat suitability and geographic distribution of the species in the two regions. We conducted surveys in Anjouan and Moheli, Comoros Islands (October–December 2017, February–April 2018 and May–July 2019), and Northwest Madagascar (October and December 2012). We estimated a mean population density of 23.49 individuals/km2
along 89.90 km of line transects for the Comoros population, and 15.23 individuals/km2 along 65 km of transects for the Madagascar population. We estimated a population size of 9128 individuals in Comoros and 7270 individuals in Madagascar. According to our species distribution model, mongoose lemurs have a relativelylarge geographic range in Comoros (336 km2, ~47% of the total area of Anjouan and Moheli, which is 714 km2) extending over low-elevation farmlands and in forests, while the Madagascar population is restricted to the remaining natural forests (3160 km2, ~17.5% of the total area studied, which is 18,000 km2). However, high levels of hunting (Madagascar only), habitat disturbance, and conversion of natural forest into agricultural lands render the species critically endangered to extinction. As population density and the distribution of primates are highly related to the habitat quality and vegetation availability and since the high level of habitat disturbance and lemur hunting
(in Madagascar) are associated with high levels of poverty, we suggest (1) enhancing livelihoods and well-being of rural communities, which will allow them to be less dependent on natural resources and reduce unsustainable natural resource use, (2) involving a broad community of local individuals and entities in conservation and management, and (3) restoring forests and avoiding the conversion of secondary forest into agricultural lands. Our fndings highlight how population density and distribution patterns are related to environmental factors. They also emphasize how species distribution modeling approaches are useful for primate conservation.

Citation:

Ibouroi MT, Dhurham S.A.O. Rabarivola Clément 2022. Habitat suitability and population size estimates for the mongoose lemurs (Eulemur mongoz) of Madagascar and the Comoro Islands and implications for their conservation. International Journal of Primatology. DO: https://doi.org/10.1007/s10764-022-00318-7

Abstract

The Grande Comoro Scops Owl (Otus pauliani) is an endangered, rare and elusive owl species restricted to the Karthala  forest, Grande Comore. This scops owl species is listed among the most threatened animals of the Comoro archipelago. The  species is subjected to strong anthropogenic pressures causing a high rate of habitat loss. Little is known about the species’ population size, habitat suitability and geographic distribution, making the establishment of relevant conservation strategies difcult. In this study we assessed the population density and abundance of the species using the distance sampling approach through (1) the conventional distance sampling method (CDS), and (2) density surface modeling (DSM). Based on DSM, we applied a species distribution modeling method to investigate habitat suitability and geographic distribution of the species to close this knowledge gap. Average population density was estimated to be ca. 27 individuals km−2. We estimated a global population size of 3452 individuals. Our DSM suggested that the Grande Comoro Scops Owl has a very limited distribution (133 km2), restricted to high elevations in Grande Comore’s remaining natural forests (between 800 and 2000 m altitude). However, the currently high level of habitat disturbance and conversion of natural forest into agricultural land could render the species vulnerable to extinction. To ensure the viability of the species and the biodiversity of the Karthala forest, we suggest (1) restoring forest and securing corridors in the Karthala remnant forest; (2) avoiding the conversion of secondary forest into agricultural land, and using existing agroforestry for plantation development; (3) involving a broad community of local individuals and entities in their conservation and management.

Citation

Ibouroi M.T, Ali-Hassane N, Moindjié S, Ombade M, Mohamed N, Hamidou[1]Saidou M, Abderemane K, Ali Cheha A. 2019. The first comprehensive survey of habitat suitability and population size for the endangered Grande Comoro Scops Owl (Otus pauliani): implications for its conservation. Journal of Ornithology. 160:1121– 1132 https://doi.org/10.1007/s10336-019-01689-0

Abstract
Pteropus livingstonii and Pteropus seychellensis comorensis are endemic fruit bat species that are among the most threatened animals in the Comoros archipelago. Both species are pollinators and seed dispersers of native and cultivated plants and are thus of crucial importance for the regeneration of natural forests as well as for cultivated plantations. However, these species are subject to strong anthropogenic pressures and face one of the highest rates of natural habitat loss reported worldwide. Yet little is known about the population genetic structure of these two species, making it difficult to define relevant conservation strategies. In this study, we investigated for the two flying fox species (1) the level of genetic diversity within islands, as well as across the archipelago and (2) the genetic structure between the two islands (Anjouan and Mohéli) for P. livingstonii and between the four islands of the archipelago (Anjouan, Mohéli, Grande Comore and Mayotte) for P. s. comorensis using mitochondrial and microsatellite markers. The results revealed contrasting patterns of genetic structure, with P. s. comorensis showing low genetic structure between islands, whereas P. livingstonii exhibited high levels of inter-island genetic differentiation. Overall, the genetic analyses showed low genetic diversity for both species. These contrasting genetic patterns may be the result of different dispersal patterns and the populations’ evolutionary histories. Our findings lead us to suggest that in terms of conservation strategy, the two populations of P. livingstonii (on Anjouan and Mohéli islands) should be considered as two separate management units. We recommend focusing conservation efforts on the Anjouan population, which is the largest, exhibits the highest genetic diversity, and suffers the greatest anthropogenic pressure. As for P. s. comorensis, its four populations could be considered as a single unit for conservation management purposes. For this species, we recommend protecting roosting trees to reduce population disturbance.