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opencc-zeroAug 2020View details →

Irreversible habitat specialization does not constrain diversification in hypersaline water beetles

Specialization to extreme environments is often considered an evolutionary dead-end, leading to irreversible adaptations and reduced evolvability. There is, however, mixed evidence of this macroevolutionary pattern, and limited data from speciose lineages. Here, we tested the effect of habitat specialization to hypersaline waters in the diversification rates of aquatic beetles of the genus Ochthebius (Coleoptera, Hydraenidae), using a molecular phylogeny with more than 50% of the 546 recognized species, including representatives of all subgenus and species groups but one. Phylogenies were built combining mitochondrial and nuclear genes, with the addition of 42 mitochondrial genomes. Using Bayesian methods of character reconstruction, we show that hypersaline tolerance is an irreversible ecological specialization that arose multiple times independently. Two lineages of Ochthebius experienced a significant increase in diversification rates, one of them inhabiting hypersaline waters, but there was no overall correlation with habitat or any significant decrease in diversification rates despite the irreversibility of the hypersaline tolerance. Our study tested for the first time the impact of hypersaline habitat specialization on diversification rates, without support of being an evolutionary dead-end. On the contrary, multiple and ancient lineages fully adapted to these extreme osmotic conditions seem able to diversify over long evolutionary periods.

opencc-zeroOct 2020View details →

Data from: Historical demography of four gecko species specializing in boulder cave habitat – its implications in the evolutionary dead end hypothesis and conservation

Specialization in narrow ecological niches might not only help species to survive in competitive or unique environments but also contribute to their extermination over evolutionary time. Although the "evolutionary dead end" hypothesis has long been debated, empirical evidence from species with detailed information on niche specialization and evolutionary history is still rare. Here we used a group of four closely related Cnemaspis gecko species that highly depend on granite boulder caves in the Mekong Delta to illuminate the potential impact of ecological specialization on their evolution and population dynamics. Isolated by the unsuitable habitat of a flood plain, these boulder-dwelling geckos are among the most narrowly distributed Squamata species in the world. We applied several coalescence-based approaches combined with the RAD-seq technique to estimate their divergence times, gene flow and demographic fluctuations during the speciation and population differentiation processes. Our results showed long-term population shrinkage in the four geckos and limited gene flow during their divergence. The results suggest that the erosion and fragmentation of the granite boulder hills have had great impacts on these populations' divergences and population declines. We argue that the specialist gecko's habitat specialization has facilitated the fine-scaled speciation in these granite rocky hills; in contrast, specialization might also have pushed these species toward the edge of extinction. Our study also emphasizes the conservation urgency of these vulnerable, cave-dependent geckos.

opencc-zeroDec 2017View details →

Data from: Molecular signatures of host specificity linked to habitat specialization in Exaiptasia sea anemones.

Rising ocean temperatures associated with global climate change induce breakdown of the symbiosis between coelenterates and photosynthetic microalgae of the genus Symbiodinium. Association with more thermotolerant partners could contribute to resilience, but the genetic mechanisms controlling specificity of hosts for particular Symbiodinium types are poorly known. Here we characterize wild populations of a sea anemone laboratory model system for anthozoan symbiosis, from contrasting environments in Caribbean Panama. Patterns of anemone abundance and symbiont diversity were consistent with specialization of holobionts for particular habitats, with Exaiptasia pallida/S. minutum (ITS2 type B1) abundant on vertical substrate in thermally stable, shaded environments but E. brasiliensis/Symbiodinium sp. (ITS2 clade A) more common in shallow areas subject to high temperature and irradiance. Population genomic sequencing revealed a novel E. pallida population from the Bocas del Toro Archipelago that only harbors S. minutum. Loci most strongly associated with divergence of the Bocas-specific population were enriched in genes with putative roles in cnidarian symbiosis, including activators of the complement pathway of the innate immune system, thrombospondin-type-1 repeat domain proteins, and coordinators of endocytic recycling. Our findings underscore the importance of unmasking cryptic diversity in natural populations and the role of long-term evolutionary history in mediating interactions with Symbiodinium.

opencc-zeroMar 2022View details →

Reduced genetic diversity associated with the northern expansion of an amphibian species with high habitat-specialization, Ascaphus truei, resolved using two types of genetic markers

Reconstruction of historical relationships between geographic regions within a species' range can indicate dispersal patterns and help predict future responses to shifts in climate. Ascaphus truei (coastal tailed frog) is an indicator species of the health of forests and perennial streams in the Coastal and Cascade Mountains of the Pacific Northwest of North America. We used two genetic techniques — microsatellite and genotype-by-sequencing (GBS) — to compare the within region genetic diversity of populations near the northern extent of the species' range (British Columbia, Canada) to two geographic regions in British Columbia and two in Washington, USA, moving towards the core of the range. Allelic richness and heterozygosity declined substantially as latitude increased. The northernmost region had the lowest mean expected heterozygosities for both techniques (microsatellite, M = 0.20, SE = 0.080; GBS, M = 0.025, SE = 0.0010) and the southernmost region had the highest (microsatellite, M = 0.88, SE = 0.054; GBS, M = 0.20, SE = 0.0029). The northernmost regions (NC and MC) clustered together in population structure models for both genetic techniques. Our discovery of reduced diversity may have important conservation and management implications for population connectivity and the response of A. truei to climate change.

opencc-zeroMay 2022View details →

Data from: Habitat change and its consequences on reef fish specialization in biogeographic transition zones

Aim Reef fishes are commonly recognized as sentinels of the ongoing tropicalization in biogeographic transition zones between temperate and tropical areas. Despite the reliance of these marine ectotherms on the benthos, the importance of benthic habitat has rarely been considered as a factor constraining fish distribution. Therefore, our study aims at examining the consequences of both temperature and benthic variations on the fish fauna and diagnosing potential sentinels of these environmental changes. Location Taiwan, West Pacific. Taxon Teleostei (184 species). Methods We examined how the partitioning of habitats can influence the specialization of fish fauna along a latitudinal gradient. We diagnosed 'specialist' and 'generalist' fishes in this partitioning. For each specialist, we further evaluated whether its distribution is constrained by temperature, benthic habitat, or both factors combined. The change in sea surface temperature over the last three decades was also monitored. Results Fish fauna showed the highest specialization when tropical and subtropical partitions of habitat were considered. Fifty-one tropical specialists, seven subtropical specialists, and 21 possible generalists were identified. Among specialists, 13 species were associated with temperature, 19 with habitat, and 26 with both factors. Steady warming occurred across latitudes but was accentuated in the winter of subtropical habitat. Main conclusions Our results suggested that the distribution of some specialist fishes was constrained only by temperature while the distribution of some others also depended on the availability of benthic habitats. Consequently, under global warming, the distribution of some specialists might shift in a manner that follows the movement of isotherms, while the distribution of others might also be conditioned by the poleward shifts of benthos. A temporal mismatch between the emergence of suitable thermal environments and the arrival of some specialists may exist. Therefore, the tropicalization of high-latitude areas may be characterized by different waves of colonization.

publicMar 2022View details →

Reduced genetic diversity associated with the northern expansion of an amphibian species with high habitat-specialization, Ascaphus truei, resolved using two types of genetic markers

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publicDec 2025View details →

Data from: Specific island biogeographic and landscape features shape plant diversity and habitat specialism on edaphic quartz islands in an arid ocean

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publicAug 2020View details →

Irreversible habitat specialization does not constrain diversification in hypersaline water beetles

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publicMar 2019View details →

Data from: Molecular signatures of host specificity linked to habitat specialization in Exaiptasia sea anemones.

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publicOct 2020View details →

Data from: Historical demography of four gecko species specializing in boulder cave habitat – its implications in the evolutionary dead end hypothesis and conservation

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publicJun 2022View details →

Data from: Habitat change and its consequences on reef fish specialization in biogeographic transition zones

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Growth, gas exchange and hydraulic conductivity of greenhouse grown willows under pre-drought conditions: Investigating patterns of habitat specialization in fifteen co-occurring willow and poplar species.

Thirteen willow (Salix) species occur in southeastern Minnesota and often co-occur within the same wetlands. This high local diversity is challenging to explain since closely related species are often functionally similar and density-dependent interactions such as competition and susceptibility to pests and pathogens should limit their co-occurrence. However, if willow species are partitioning resources, or if they are phylogenetically structured so that closely related species rarely co-occur, then the impact of these density-dependent processes could be reduced. In this study, I examined the role of niche partitioning in maintaining local willow diversity by documenting species distributions in plots across a water availability gradient and comparing species physiology in the field and greenhouse. By taking a phylogenetic approach, I also investigated whether willow communities exhibit phylogenetic community structure and whether there is evidence for environmental filtering.

Functional traits measured in a greenhouse common garden: Investigating patterns of habitat specialization in fifteen co-occurring willow and poplar species.

Sequences of the nuclear gene ADH for thirteen species of willows and two poplars: Investigating patterns of habitat specialization in fifteen co-occurring willow and poplar species.

Functional traits measured under field conditions in native populations: Investigating patterns of habitat specialization in fifteen co-occurring willow and poplar species.