Long-term Habitat Fragmentation Research Articles

Contrasting genetic and morphological differentiation among geographical lineages of a stenotopic miniature rasborine, Boraras maculatus, in Peninsular Malaysia.

The variability in the stenotopic miniature rasborine Boraras maculatus (Cypriniformes: Danionidae: Rasborinae) across acidic-water habitats of Peninsular Malaysia (PM) was investigated using two molecular markers (the mitochondrial cytochrome c oxidase subunit I [COI] gene and the nuclear rhodopsin gene), as well as morphological evidence. Molecular phylogenetic analyses revealed differentiation among populations of B. maculatus in PM with the distinction of four allopatric lineages. Each of them was recognized as a putative species by automatic species delimitation methods. These lineages diverged from each other between 7.4 and 1.9 million years ago. A principal component analysis (PCA) was conducted to examine the multivariate variation in 11 morphometric measurements among three of these lineages. PCA results showed a significant overlap in morphological characteristics among these lineages. Additionally, a photograph-based machine learning approach failed to fully differentiate these lineages, suggesting limited morphological differentiation. B. maculatus represents a case of morphological stasis in a stenotopic miniature species. Strong habitat preference, coupled with long-term habitat fragmentation, may explain why each lineage of B. maculatus has a restricted distribution and did not disperse to other regions within and outside of PM, despite ample possibilities when the Sunda shelf was emerged and drained by large paleodrainages for most of the past 7 million years. The conservation status of B. maculatus and its peat swamp habitats are discussed, and it is concluded that peat swamps comprise several evolutionary units. Each of these units is considered a conservation unit and deserves appropriate protection.

Long-Term Habitat Fragmentation Is Associated With Reduced MHC IIB Diversity and Increased Infections in Amphibian Hosts

Habitat fragmentation and wildlife disease are two widespread drivers of biodiversity loss, yet few empirical studies have explored their interactions. In this study, we utilized a naturally fragmented island system to examine the impacts of fragmentation on genetic diversity and amphibian infection dynamics. We determined the impacts of fragmentation on genetic diversity at the immunity locus MHC IIB, a hypothesized predictor of disease susceptibility. Contrary to expectations, island populations lost genetic diversity at this locus while simultaneously experiencing positive selection at MHC IIB. We then used Next-Generation Sequencing to identify a variety of potential eukaryotic parasites from amphibian skin swabs. Island populations exhibited higher potential parasite richness (proportion of eukaryotic microbe operational taxonomic units or OTUs from parasitic taxa) relative to mainland populations. MHC homozygotes hosted a lower diversity of potential parasites, and population-level MHC diversity was negatively associated with parasite richness. Our results show that genetic erosion can occur at the MHC IIB locus following fragmentation, which may contribute to increased susceptibility to parasites.

Births during 7years after the translocation of a pair of black-and-gold howler monkeys (Alouatta caraya) to a forest fragment in southeast Brazil.

Fecundity in female primates is influenced by the nutritional condition. If when translocated howler monkeys exhibit the same breeding patterns as non-translocated members of the same genus, it is an indication that the translocated monkeys have become well adapted to their release site and that they are likely in good nutritional condition. The objective of this study was therefore to investigate this pattern by recording copulations (over 5years) and births (over 7years) after the translocation of a pair of black-and-gold howler monkeys (Alouatta caraya) and to evaluate their gestation period, seasonality of births, and intervals between births. The pair was released in November 2009 on the campus of the University of São Paulo in Ribeirão Preto, São Paulo State, Brazil. Data on copulations were collected from January 2010 to March 2011 and from January 2012 to December 2014. Births were collected from January 2010 to December 2016. During the 5-year observation period, 25 copulations were recorded. Seven births were recorded over a period of 7years, which included reproduction of the offspring of the translocated pair. Births occurred in the dry season between April and August. The interval between births was approximately 1year. Our data provide insight into the reproduction of howler monkeys that have been translocated to a new habitat. Translocation can provide a valuable approach for rescuing or restoring Alouatta, whose populations have been detrimentally impacted by long-term habitat fragmentation.

Differential and delayed response of two ant species to habitat fragmentation via the introduction of a pine matrix

1. Ants are a ubiquitous and crucial component of Australian Eucalyptus forests, but responses to long-term habitat fragmentation remain poorly understood. Two ant species were followed across a 21-year history of pine plantation establishment and maturation in a southeast Australian Eucalyptus forest. 2. At Wog Wog in southeastern Australia, a Native Eucalyptus forest was clear-cut to make way for plantation establishment and 12 remnant patches of forest were left intact and subsequently surrounded by a pine matrix. Pitfall traps were placed in the continuous native forest, remnant Eucalyptus patches, and the pine matrix between fragments, and were stratified based on proximity to remnant patch edges and habitat type. Two ant species are focused on that represent the only remaining data for the early years of the experiment. 3. While Leptomyrmex erythrocephalus (Fabricius), the rarer of the two species, was not affected by fragmentation in the short term, 21 years after fragmentation, it was less likely to occur in both the mature pine matrix and fragments than in continuous forest controls. Aphaenogaster longiceps (Smith F.) was equally likely to occur in the fragments, continuous forest, and pine matrix early in the experiment but by year 21 post-fragmentation was less likely to occur in the pine matrix than fragments or controls. 4. Importantly, we only detected negative impacts of fragmentation on ant occurrence as the pine plantation matrix matured and isolated ant populations on fragments. 5. It is concluded that changes in matrix suitability and specific habitat characteristics influence ant persistence in Eucalyptus fragments.

The effect of long-term historical habitat fragmentation on genetic diversity of the relictual conifer Calocedrus macrolepis (Cupressaceae) in China

Geological events and glacial history have all induced habitat fragmentation, which has long been recognized as a major threat to the survival of many species. However, fragmentation has differential effects on population genetic patterns of individual species, such as loss of genetic diversity, genetic differentiation enhance, inbreeding increase, allelic deletion, and no effect. Calocedrus macrolepis Kurz is an endangered ancient relictual and fragmented conifer. In this study, the genetic diversity and structure were analyzed to shed light on the factors that determine their contemporary genetic patterns and to provide optimum strategies for future conservation. The genetic diversity within and among 14 extant populations of C. macrolepis was analyzed using nine microsatellite markers. The genetic diversity (H E = 0.636), genetic differentiation (F ST = 0.163), and gene flow (Nm = 1.496) were disclosed, respectively. No significant correlation was detected by the Mantel test between genetic and geographical distances among pair-wise comparisons of populations (r = 0.197, P = 0.103). Fourteen populations could be generally assigned to two separate groups, and significant asymmetrical migration among populations within the regional groups was revealed. Both Quaternary glaciations and neotectonic movements seem to be associated with a long history of population contraction and fragmentation of C. macrolepis, enhancing its genetic drift and population divergence. The results indicate that long-term habitat fragmentation could be responsible for the genetic structure observed. In situ conservation strategies should be designed, especially small and isolated populations. Also, special attention should be given to populations LY and DZ because of their private alleles, as well as to population CJ isolated from the mainland.

Genetic effects of chronic habitat fragmentation revisited: Strong genetic structure in a temperate tree, Taxus baccata (Taxaceae), with great dispersal capability

Tree species are thought to be relatively resistant to habitat fragmentation because of their longevity and their aptitude for extensive gene flow, although recent empirical studies have reported negative genetic consequences, in particular after long-term habitat fragmentation in European temperate regions. Yet the response of each species to habitat loss may differ greatly depending on their biological attributes, in particular seed dispersal ability. In this study, we used demographic and molecular data to investigate the genetic consequences of chronic habitat fragmentation in remnant populations of Taxus baccata in the Montseny Mountains, northeast Spain. The age structure of populations revealed demographic bottlenecks and recruitment events associated with exploitation and management practices. We found a strong genetic structure, both at the landscape and within-population levels. We also detected high levels of inbreeding for a strictly outcrossing species. Chronic forest fragmentation resulting from long-term exploitation in the Montseny Mountains seems the most plausible explanation for the strong genetic structure observed. Our results support the view that, contrary to some predictions, tree species are not buffered from the adverse effects of habitat fragmentation, even in the case of species with a high dispersal potential.

Effects of long-term habitat fragmentation on a wetland bird community

The recent changes of an internationally important wetland for birds, Albuferas of Adra (Almería province, Spain), were analysed focussing on the long-term human impact on the landscape and its biological consequences for the avian community. Habitat fragmentation throughout the second half of the 20th century affected mainly the peripheral reed beds (Phragmites australis) most accessible to humans. These changes presumably caused the loss of the only nesting marsh passerines, the bird guild most dependent on emergent vegetation. More abundant species had greater capacity to occupy reed-bed patches apparently by having more colonizing individuals than did rarer species. Conservation, creation or restoration of marsh habitats in endangered and ecologically valuable wetlands are vital to maintain and recover the greatest number of marsh species, such as the threatened Moustached Warbler (Acrocephalus melanopogon) and Reed Bunting (Emberiza schoeniclus).

Long‐term isolation and recent range expansion from glacial refugia revealed for the endemic springtail Gomphiocephalus hodgsoni from Victoria Land, Antarctica

We examined the phylogeography of the endemic Antarctic collembolan Gomphiocephalus hodgsoni using allozymes and mitochondrial DNA (mtDNA; COI) to determine if potentially limited dispersal and long-term habitat fragmentation have promoted regional genetic differentiation. Allozyme analyses showed that differentiation among 21 populations within the Ross Dependency was high (FST = 0.55) with two main groups each representing a distinct geographical region: (1) Ross Island and Beaufort Island; and (2) all continental sites. Ross Island populations showed low levels of differentiation (FST = 0.05) and no correlation with geographical distance, suggesting their derivation from a single glacial refuge. By contrast, continental regions revealed moderate levels of differentiation (FST = 0.27) and a strong correlation with geographical distance, indicating a much older history with several refugia likely. Two sympatric allozyme genotypes were found at three continental sites from Taylor Valley and were congruent with two mtDNA haplotypes, implying nonrandom breeding groups. Although haplotype sharing between one Ross Island site (Cape Bird) and one continental site (Granite Harbour) was identified, the clades showed mostly fragmented allopatric distributions. The extensive Pleistocene glaciations, in conjunction with limited dispersal opportunities, appear to have promoted isolation and divergence among the fragmented habitats. Furthermore, the McMurdo Sound appears to be an effective isolating barrier to dispersal. However, we suggest that the unaided dispersal capacity of G. hodgsoni is unlikely to account for the limited mixing of haplotypes across the McMurdo Sound and recent human- or bird-mediated dispersal is highly probable.

Genetic (RAPD) diversity in Peromyscus maniculatus populations in a naturally fragmented landscape.

We assessed the effects of long-term habitat fragmentation on genetic (random amplified polymorphic DNA) diversity in 11 Peromyscus maniculatus populations in the Lake Superior watershed. We analysed genetic structure at two spatial scales and the effect of island size and isolation on genetic diversity. At the regional scale, island populations differed from mainland populations (FST = 0.36), but mainland populations did not differ from each other (FST = 0.01). At the local scale, populations of the main island of Isle Royale differed from adjacent islet populations (P < 0.001; Monte Carlo approximation of Fisher's exact test), but not from each other (combined P = 0.63). Although geographical distance and genetic distance were positively correlated (P < 0.01; Mantel test), cluster analysis revealed some inconsistencies. Finally, genetic diversity was inversely related to isolation (P = 0.01), but had an unexpectedly negative relationship with island area (P = 0.03). The genetic structure of P. maniculatus populations in portions of the Lake Superior watershed appears to have been affected by long-term habitat fragmentation.

Plant species diversity and polyploidy in islands of natural vegetation isolated in extensive cultivated lands

Natural polyploidy is often related to a longer life span, vegetative reproduction and higher competitive ability. In this paper, we test the possibility that these characteristics may favour the survival of polyploid taxa under conditions of long-term habitat fragmentation. In islands of natural vegetation isolated in extensive vineyards located in the South of France and in a large neighbouring area of natural vegetation, plant species richness and the relative abundance of polyploid taxa were assessed according to island size, isolation and vegetation structure. High species richness was observed, with numerous species restricted to the islands, suggesting that these may constitute refugia. However, species richness was not related to island size or to degree of isolation except for the flora of the woody areas. A very positive effect of area fragmentation on plant richness was observed, which is probably attributable to relatively low species overlap among the islands. Particularly high species richness was observed in open areas, provided that these were not extensively colonized by shrubs which seem to be responsible for local extinction of many annual taxa. Polyploids, which comprised mostly perennial herbs and woody species, were predominant in all the islands and in the large reference area. In open habitats invaded by shrubby species, a higher relative frequency of polyploids was observed in islands than in the reference area. Moreover, polyploid taxa were present in a larger number of islands than the diploid taxa, which were often restricted to a single island, suggesting that, after a long period of isolation, the polyploids may still have a lower probability of extinction. Evidence was obtained from vegetation structure analysis that diploid and polyploid annual herbs were restricted to open habitats and were both eliminated by shrubby species. Conversely, the diploid perennial herbs were also significantly affected by shrub colonization whereas the polyploids were mostly present in shrubby areas. This suggests that the higher competitive ability of polyploid perennial herbs may constitute a critical factor responsible for their wider distribution over the islands. We report the implications of our findings on conservation strategies, more particularly for a Mediterranean flora.