Comparing the population structure of the specialist Butler’s gartersnake (Thamnophis butleri) and the generalist eastern gartersnake (Thamnophis sirtalis sirtalis) in Ontario and Michigan

Species differing in life history attributes vary in their responses to features within a shared landscape. We evaluated genetic structure of sympatric gartersnake species in Southwestern Ontario, Canada and south-east Michigan, U.S.A., where habitat fragmentation is high due to agriculture and urbanization. We surveyed genetic structure of the habitat specialist, Butler’s gartersnake (Thamnophis butleri; Cope, 1889) and habitat generalist, eastern gartersnake (Thamnophis sirtalis sirtalis; Linnaeus, 1758) using DNA microsatellites. Bayesian clustering, Discriminant Analysis of Principal Components, and pairwise population comparisons revealed genetic differentiation among three major regional clusters of Butler’s gartersnake with evidence of further division within one. Genetic clustering of Butler’s gartersnake suggest that inhospitable habitat limits dispersal. Eastern gartersnakes showed less structure, with assignment tests implying a single genetic cluster. We found positive significant Mantel’s r for both species in the smallest distance class (<15 kms), but significant isolation by distance for Thamnophis butleri only. These findings together imply that connectivity for eastern gartersnakes is less impacted by habitat loss and fragmentation or that we were less able to detect their effects. Our study shows the value of multispecies comparisons in studies seeking to understand the underlying causes of genetic structure in natural populations.

Snakes on an African plain: the radiation of Crotaphopeltis and Philothamnus into open habitat (Serpentes: Colubridae)

Background The African continent is comprised of several different biomes, although savanna is the most prevalent. The current heterogeneous landscape was formed through long-term vegetation shifts as a result of the global cooling trend since the Oligocene epoch. The overwhelming trend was a shift from primarily forest, to primarily savanna. As such, faunal groups that emerged during the Paleogene/Neogene period and have species distributed in both forest and savanna habitat should show a genetic signature of the possible evolutionary impact of these biome developments. Crotaphopeltis and Philothamnus (Colubridae) are excellent taxa to investigate the evolutionary impact of these biome developments on widespread African colubrid snakes, and whether timing and patterns of radiation are synchronous with biome reorganisation. Methods A phylogenetic framework was used to investigate timing of lineage diversification. Phylogenetic analysis included both genera as well as other Colubridae to construct a temporal framework in order to estimate radiation times for Crotaphopeltis and Philothamnus. Lineage diversification was estimated in Bayesian Evolutionary Analysis Sampling Trees (BEAST), using two mitochondrial markers (cyt–b, ND4), one nuclear marker (c–mos), and incorporating one fossil and two biogeographical calibration points. Vegetation layers were used to classify and confirm species association with broad biome types (‘closed’ = forest, ‘open’ = savanna/other), and the ancestral habitat state for each genus was estimated. Results Philothamnus showed an ancestral state of closed habitat, but the ancestral habitat type for Crotaphopeltis was equivocal. Both genera showed similar timing of lineage diversification diverging from their sister genera during the Oligocene/Miocene transition (ca. 25 Mya), with subsequent species radiation in the Mid-Miocene. Philothamnus appeared to have undergone allopatric speciation during Mid-Miocene forest fragmentation. Habitat generalist and open habitat specialist species emerged as savanna became more prevalent, while at least two forest associated lineages within Crotaphopeltis moved into Afromontane forest habitat secondarily and independently. Discussion With similar diversification times, but contrasting ancestral habitat reconstructions, we show that these genera have responded very differently to the same broad biome shifts. Differences in biogeographical patterns for the two African colubrid genera is likely an effect of distinct life-history traits, such as the arboreous habits of Philothamnus compared to the terrestrial lifestyle of Crotaphopeltis.

Effect of Discharge on Hatching and Growth of Age-0 Black Bass in Two Southeastern U.S. Rivers

We examined the influence of variable discharge on hatching and age-0 growth for fluvial specialist and habitat generalist species of black bass Micropterus spp. in two southeastern U.S. rivers, the Flint River, Georgia (unregulated), and the Tallapoosa River, Alabama (regulated by several hydropower dams). Between 2008 and 2010, we collected 285 Largemouth Bass M. salmoides (generalist) and 254 Shoal Bass M. cataractae (specialist) from two reaches of the Flint River. In 2010–2011, we collected 309 Alabama Bass M. henshalli (generalist) and 216 Redeye Bass M. coosae (specialist) from two regulated reaches and one unregulated reach of the Tallapoosa River. Successful hatching of black bass in both rivers generally occurred from late March to early June when water levels were low and stable. Hatching distributions of all black bass were generally unimodal with little evidence of spawning disruption, except for Alabama Bass in the most-regulated reach of the Tallapoosa River, which appeared to be disrupted by large discharge events. Mean growth of both species in the Flint River varied from 0.64 to 0.82 mm/d across reaches and years; Shoal Bass generally grew faster than Largemouth Bass in all reach–year combinations. Largemouth Bass growth was inversely correlated to discharge variation in one reach, but Shoal Bass growth was not correlated to discharge variation in either reach. Alabama Bass and Redeye Bass growth rates in the Tallapoosa River were similar to rates observed for congeners in the Flint River; Alabama Bass grew faster than Redeye Bass. Growth of both species was inversely related to discharge variation in five of six reach–species combinations; the only exception was for Redeye Bass in the less-regulated reach. Results from this study suggest that variable discharge has less influence on successful reproduction of black bass than was reported for other fishes, but growth may be more affected by discharges resulting from anthropogenic sources than those associated with the natural regime.

Striking between-population floral divergences in a habitat specialized plant

When the habitat occupied by a specialist species is patchily distributed, limited gene flow between the fragmented populations may allow population differentiation and eventual speciation. ‘Sky islands’—montane habitats that form terrestrial islands—have been shown to promote diversification in many taxa through this mechanism. We investigate floral variation in Impatiens lawii, a plant specialized on laterite rich rocky plateaus that form sky islands in the northern Western Ghats mountains of India. We focus on three plateaus separated from each other by ca. 7 to 17 km, and show that floral traits have diverged strongly between these populations. In contrast, floral traits have not diverged in the congeneric I. oppositifolia, which co-occurs with I. lawii in the plateaus, but is a habitat generalist that is also found in the intervening valleys. We conducted common garden experiments to test whether the differences in I. lawii are due to genetic differentiation or phenotypic plasticity. There were strong differences in floral morphology between experimental plants sourced from the three populations, and the relative divergences between population pairs mirrored that seen in the wild, indicating that the populations are genetically differentiated. Common garden experiments confirmed that there was no differentiation in I. oppositifolia. Field floral visitation surveys indicated that the observed differences in floral traits have consequences for I. lawii populations, by reducing the number of visitors and changing the relative abundance of different floral visitor groups. Our results highlight the role of habitat specialization in diversification, and corroborates the importance of sky islands as centres of diversification.

Metabolic flexibility allows bacterial habitat generalists to become dominant in a frequently disturbed ecosystem

Ecological theory suggests that habitat disturbance differentially influences distributions of habitat generalist and specialist species. While well-established for macroorganisms, this theory has rarely been explored for microorganisms. Here we tested these principles in permeable (sandy) sediments, ecosystems with much spatiotemporal variation in resource availability and physicochemical conditions. Microbial community composition and function were profiled in intertidal and subtidal sediments using 16S rRNA gene amplicon sequencing and metagenomics, yielding 135 metagenome-assembled genomes. Community composition and metabolic traits modestly varied with sediment depth and sampling date. Several taxa were highly abundant and prevalent in all samples, including within the orders Woeseiales and Flavobacteriales, and classified as habitat generalists; genome reconstructions indicate these taxa are highly metabolically flexible facultative anaerobes and adapt to resource variability by using different electron donors and acceptors. In contrast, obligately anaerobic taxa such as sulfate reducers and candidate lineage MBNT15 were less abundant overall and only thrived in more stable deeper sediments. We substantiated these findings by measuring three metabolic processes in these sediments; whereas the habitat generalist-associated processes of sulfide oxidation and fermentation occurred rapidly at all depths, the specialist-associated process of sulfate reduction was restricted to deeper sediments. A manipulative experiment also confirmed habitat generalists outcompete specialist taxa during simulated habitat disturbance. Together, these findings show metabolically flexible habitat generalists become dominant in highly dynamic environments, whereas metabolically constrained specialists are restricted to narrower niches. Thus, an ecological theory describing distribution patterns for macroorganisms likely extends to microorganisms. Such findings have broad ecological and biogeochemical ramifications.

Habitat generalist species constrain the diversity of mimicry rings in heterogeneous habitats

How evolution creates and maintains trait patterns in species-rich communities is still an unsolved topic in evolutionary ecology. One classical example of community-level pattern is the unexpected coexistence of different mimicry rings, each of which is a group of mimetic species with the same warning signal. The coexistence of different mimicry rings in a community seems paradoxical because selection among unpalatable species should favor convergence to a single warning pattern. We combined mathematical modeling based on network theory and numerical simulations to explore how different types of selection, such as mimetic and environmental selections, and habitat use by mimetic species influence the formation of coexisting rings. We show that when habitat and mimicry are strong sources of selection, the formation of multiple rings takes longer due to conflicting selective pressures. Moreover, habitat generalist species decrease the distinctiveness of different mimicry rings’ patterns and a few habitat generalist species can generate a “small-world effect”, preventing the formation of multiple mimicry rings. These results may explain why the coexistence of mimicry rings is more common in groups of animals that tend towards habitat specialism, such as butterflies.

Living on polluted habitat: A preliminary study of marine debris impact to foraging waterbirds in Muara Angke Mangrove Ecosystem, Jakarta

Mangrove ecosystems are vulnerable to pollution such as marine debris. The presence of marine debris can affect the waterbird community. The present study aims to determine and analyze the effect of marine debris on waterbirds in the Muara Angke Mangrove Area. The research was undertaken from October to November 2020 at three research areas: Angke-Kapuk Protection Forest, Angke-Kapuk Nature Tourism Park, and Muara Angke Arboretum. Observations of waterbirds were carried out using the point count method and observations of marine debris density were conducted with the shoreline survey method developed by NOAA. To find out the pattern of marine debris distribution and its effect on waterbirds, we implemented Principal Component Analysis (PCA) and Spearman Correlation. In total, there were 13 species of waterbirds from 7 different orders in the three research areas. PCA analysis showed 6 variables in PC1 namely herbivorous duck, tactical surface, visual surface, habitat generalist, moderate specialist, and large. Further, PC2 produces 6 variables, namely pursuit diving, stalking, habitat generalist, aquatic generalist, and large. The results of the Spearman correlation indicated that three bird species were significantly negatively correlated with trash, those species are Anhinga melanogaster, Egretta garzetta, and Mycteria cinerea.

DIVERSITY AND HABITAT PREFERENCE OF ODONATE IN CHAKRASHILA WILDLIFE SANCTUARY, WESTERN ASSAM, INDIA

The study was conducted in Chakrashila Wildlife Sanctuary of western Assam to explore diversity and habitat preference of odonata (both dragonflies and damseldly) from April 2018 to March 2019. During study period we recorded total 57 species of odonate from 39 genera and 8 families out of which, dragonfly (Anisoptera) represented by 37 species and damselfly (Zygoptera) represented by 20 species. Suborder Zygoptera were represented by the families Chlorocyphidae, Coenagrionidae, Platycnemididae, Euphaeidae, Calopterygidae and suborder Anisoptera by the Aeshnidae, Gomphidae and Libellulidae. Libellulidae was the largest family with 29 species, while Chlorocyphidae and Euphaeidae represent only single species. Among the five habitats highest species were recorded from wetland (63%) and lowest from dense forest (41%) while 20 species were recognized as habitat specialist and 7 species were habitat generalist.

Dhole Cuon alpinus in Satchari National Park: on the first verifiable evidence from northeast Bangladesh

The distribution range of the globally Endangered dhole Cuon alpinus overlaps mixed evergreen mid-hill forests of northeastern Bangladesh but lacks any authentic documentation. With the first evidence from this region, we observed the activity pattern of dhole, of its prey and of human activities in Satchari National Park, a part of a larger northeastern forested area, Raghunandan Hill Reserve Forest – the northernmost fringe of the Baramura Hills of India. We obtained 32 photos of solitary individuals on eight different events from six out of 587 camera trap days. Naïve occupancy estimate for dhole was 0.41 with a detection probability of 0.65. We identified two individuals, and reported five predation events. We encountered a moderately high temporal overlap of dhole activity with that of barking deer (∆̂1 = 0.65, CI = 0.42–0.83), human activity (0.63, 0.38–0.89), and livestock movement (0.59, 0.38–0.89). Given that dhole is a diurnal hyper-carnivore, illegal logging and tourism pressure appeared as major disturbances to the species' existence in the park. Habitats of northeastern protected forests, their adjacency with hill ranges of Tripura, and dhole being a habitat generalist, we conjecture its presence in the entire region and recommend thorough camera-trapping efforts.