Generalist Species Research Articles

Umbrella index as a conservation tool across pondscapes: A case study using frogs, aquatic insects, and plants in South Africa

Biological surrogates are valuable for conservation when they are easy and cost-effective to sample, sensitive to anthropogenic change, and show similar assemblage patterns to other taxa. The umbrella index (UI) developed by Fleishman et al. (2000), aims to conserve most species in an ecosystem by focusing on a single or small group of co-occurring species to represent all species present. Here we focus on various lentic aquatic insects (‘aquatic insects’ henceforth refers to aquatic beetles, aquatic bugs, and dragonfly larvae), adult dragonflies, frogs, and aquatic plants as potential surrogates for pond communities in the Midlands, KwaZulu-Natal Province, South Africa. There were some cross-taxon correlations, but these were too weak to consider for surrogacy, largely due to dissimilar responses to the same environmental gradients. However, using UI we identified five dragonfly species, nine aquatic insect species, and three frog species as potential umbrella groups for their own taxa. The UI for same-group surrogates was flexible and covered most taxa, ranging from co-occurring habitat generalists to rare specialist species. Furthermore, all four endemic species sampled here were effective surrogate species for other local taxa, with two of them ranking top in their own taxonomic group. The lack of congruence among the different taxa means that one taxon cannot be used to stand in for another. However, the UI allowed efficient site prioritization, so long as a multi-taxon approach is used. We recommend the UI approach when selecting surrogates to represent aquatic fauna within a pondscape of the Midlands of South Africa.

A Lankan invasion? An intriguing case of the presence of a Sri Lankan endemic skink on the southwestern Indian Coast

The biota of the Indian subcontinent is a result of Gondwanan vicariance to some extent but largely through multiple faunal exchanges between neighbouring regions. However, in recent times, humans have influenced regional biotas through the human-mediated transport of many generalist species. In this study, we report populations of Lankascincus fallax, a skink species supposedly endemic to Sri Lanka, from the west coast of Kerala in India. We conducted morphological and genetic analysis to ascertain the identity of this species and to check whether the Indian population is monophyletic. We then performed a divergence dating analysis to test whether the presence of this population is a result of ancient dispersal into India or a result of more recent events. Additionally, we used species distribution modelling to test whether the Indian L. fallax is a result of natural dispersal into India during the past (mid-Pliocene to the last glacial maximum) when there were possible land bridges between India and Sri Lanka. We find that the Indian population is nested within the Sri Lankan L. fallax and that this population diverged from the Sri Lankan population very recently, during the Pleistocene. We do not find climatic suitability between the Indian west coast and Sri Lanka under current climatic conditions, or during the past suggesting no suitable dispersal corridors between India and Sri Lanka. Overall, we hypothesize that the Indian populations of L. fallax are likely a result of human-mediated transport into India and subsequent dispersal across the west coast of Kerala.

Wildlife resilience in an urban landscape: understanding land-use impacts in Cape Town

AbstractUrbanisation is rapidly transforming and fragmenting natural habitats, disrupting ecosystems and negatively impacting biodiversity. The City of Cape Town (CoCT) is situated in a global biodiversity hotspot, but sustained anthropogenic activities have resulted in the local extirpation of most medium and large mammals. A recent survey of mammals within urban protected areas of CoCT revealed that a few, mostly medium-sized generalist species, persist. It is uncertain which native mammal species, if any, inhabit the unprotected green belts and parks in suburban and urban areas of the city. A total of 37 camera trap sites were established along four transects for a period of four months between 31 January and 31 May 2022. A total of 12 terrestrial mammal species were detected, nine of which were wild native mammals and three domestic species. Most detections were in natural habitat followed by suburban, with urban areas having the lowest detection rate of wildlife. Single season hierarchical multi-species occupancy models revealed that tree cover had a significant positive effect on both community and individual species occupancy. Contrary to our predictions, neither human population density nor the extent of the impervious surface at sites significantly affected occupancy. Cape grysbok (Raphicerus melanotis) were significantly more likely to occur at sites with a higher proportion of impervious surfaces supporting other recent research, which showed this species together with water mongoose (Atilax paludinosus) and Cape porcupine (Hystrix africaeaustralis) are one of only a few native mammals that appear to persist and may even thrive in human-modified landscapes. Our findings underscore the complexity of urban biodiversity conservation and the species-specific responses to environmental factors, emphasising the importance of tree cover in urban wildlife management.

Generalist species exhibit more genetic structure in comparison to a habitat specialist: Evidence from a phylogeographic study of two freshwater crabs (Decapoda: Potamonautidae: Potamonautes), implications for habitat conservation.

During the present study, the phylogeography of the wetland specialist, freshwater crab, Potamonautes flavusjo, was investigated and compared to that of the ubiquitous, generalist, P. sidneyi, using DNA sequence data from the mitochondrial cytochrome oxidase subunit one (COI). We inferred the evolutionary history of each species and compared their population-level genetic structure by constructing haplotype networks and using an analysis of molecular variation. Additionally, we explored the evolutionary relationship between southern African lentic and lotic freshwater crab species by examining the usefulness of carapace attributes in relation to genetic indices and a species' assumed dispersal capacity. In the lentic species, P. flavusjo, a single interconnected haplocluster characterized by shared haplotypes was observed, suggesting marked maternal dispersal, a result corroborated by the low F ST values. In contrast, for the lotic species, P. sidneyi two distinct haploclusters and marked genetic differentiation was observed indicating the absence of maternal dispersal, a result corroborated by the high F ST values. The phylogenetic relationship in P. sidneyi was further investigated using a maximum likelihood and Bayesian inference analyses with the addition of sequence data from the mitochondrial 16S rRNA locus to estimate divergence times. Three species delimitation methods (ASAP, PTP, and bGMYC) were used to explore the presence of distinct lineages in P. sidneyi. The phylogenetic results indicated that within P. sidneyi two clades were present, while divergence time estimates suggest cladogenesis during the middle to late Pleistocene. The species delimitation methods used showed moderate congruence, however all oversplit the number of putative lineages. Our results indicated that P. sidneyi is a species complex comprised of two cryptic lineages, occurring in sympatry contemporarily possibly alluding to secondary contact. Carapace height was found to have no discernible influence on the genetic indices and presumed dispersal capabilities of mainland southern African freshwater crab species. The importance of our results are discussed in terms of conservation of freshwater habitats.

Mercury contamination and potential health risk to French seabirds: A multi-species and multi-site study

Mercury (Hg) is a naturally occurring highly toxic element which circulation in ecosystems has been intensified by human activities. Hg is widely distributed, and marine environments act as its main final sink. Seabirds are relevant bioindicators of marine pollution and chicks are particularly suitable for biomonitoring pollutants as they reflect contamination at short spatiotemporal scales. This study aims to quantify blood Hg contamination and identify its drivers (trophic ecology inferred from stable isotopes of carbon (δ13C) and nitrogen (δ15N), geographical location, chick age and species) in chicks of eight seabird species from 32 French sites representing four marine subregions: the English Channel and the North Sea, the Celtic Sea, the Bay of Biscay and the Western Mediterranean. Hg concentrations in blood ranged from 0.04 μg g−1 dry weight (dw) in herring gulls to 6.15 μg g−1 dw in great black-backed gulls. Trophic position (δ15N values) was the main driver of interspecific differences, with species at higher trophic positions showing higher Hg concentrations. Feeding habitat (δ13C values) also contributed to variation in Hg contamination, with higher concentrations in generalist species relying on pelagic habitats. Conversely, colony location was a weak contributor, suggesting a relatively uniform Hg contamination along the French coastline. Most seabirds exhibited low Hg concentrations, with 74% of individuals categorized as no risk, and < 0.5% at moderate risk, according to toxicity thresholds. However, recent work has shown physiological and fitness impairments in seabirds bearing Hg burdens considered to be safe, calling for precautional use of toxicity thresholds, and for studies that evaluate the impact of Hg on chick development.

Mycobiota of the planned protected area Nyuk Lake (Republic of Karelia, Russia)

The article reports the results of macrofungi surveys in the planned protected area Lake Nyuk (pPA), situated in the north-west of the Republic of Karelia. The forests there are primarily north-boreal pine stands with pine trees aged 170—250 years at maximum. As of now, records from the pPA include 183 species of 114 genera of aphyllophoroid and agaricoid fungi. The annotation for each species specifies their habitats and occurrence. Seven species are reported for the biogeographical province Karelia pomorica occidentalis for the first time; of which two species, Hydnellum gracilipes and Tubulicrinis medius, are first records for the Republic of Karelia. The territory was found to harbor nine fungal species (Anthoporia albobrunnea, Diplomitoporus crustulinus, Flavidoporia mellita, Gloeophyllum protractum, Resinoporia crassa, Rhodonia placenta, Sidera lenis, Skeletocutis sajanensis, S. stellae) red-listed in the Republic of Karelia (2020). Locations of 13 indicator species and 16 specialist species of biologically valuable forests are known within the pPA. The findings are validated by the herbarium specimens stored at the Karelian Research Centre RAS Herbarium (PTZ) and Botanical Museum of the University of Helsinki (H). The rationale for establishing a nature conservation area in the territory is provided.

Impact of the extreme 2015-16 El Niño climate event on forest and savanna tree species of the Amazonia-Cerrado transition

Extreme drought events, driven by the El Niño Southern Oscillation (ENSO), are linked to increased tree mortality and alterations in vegetation structure, dynamics, and floristic composition in tropical forests. Existing analyses, primarily focusing on Africa, Central America, and Amazonia, overlook the floristic impacts on biome transitions. This study evaluates the profound effects of the severe 2015/2016 ENSO event on tree density and floristic composition in the critical transition zone between Amazonia and Cerrado, South America's largest biomes. Our findings not only document significant biodiversity loss but also offer insights into species resilience, guiding conservation strategies under changing climate conditions. We inventoried long-term plots before and after the extreme drought event, sampling 12,465 individuals from 526 species, 224 genera, and 65 families, in Open Ombrophilous Forest (OF), Seasonal Forest (SF), Cerradão (CD), and Typical Cerrado (TC). We document the disappearance from our plots of 97 species after the ENSO, with only 61 new species being recorded. The total loss of individuals across the transition zone was almost 10 %. The SF and CD forest plots showed the greatest replacements, species losses, and reductions in tree density. Their markedly seasonal baseline climate probably drove these changes. In most phytophysiognomies, there was an increase in pioneer species and drier environment habitat specialist species, indicating that although many species are vulnerable to extreme climate events, others benefit, especially those with a short life cycle. We found that the vegetation of the Amazonia-Cerrado transition overall is vulnerable to climate anomalies, with widespread loss of tree density and change in floristic composition. Our study also provides a species-by-species list of the most vulnerable and resistant trees which helps point to overall climate change vulnerabilities and assist with initiatives to recover degraded areas.

Network analyses show horizontal and vertical distribution of vascular epiphytes on their hosts in a fragment of cloud forest in Central Mexico.

Cloud forests figure as one of the most diverse ecosystems, accounting not only for a high number of plant species but also with a great variety of interactions among them. A common interaction in these forests is the one between vascular epiphytes and their hosts. However, few studies have used the network approach to analyze them. Here, we analyze the horizontal and vertical structure of the vascular epiphyte - host network in a cloud forest in central Mexico. We quantified the number of epiphyte stands on each host both total and per-stratum. Complete network, group, and species metrics were estimated at both levels of analysis. The host - epiphyte networks had relatively low network size but were highly connected; moderately nested, with low specialization, and modularity; but higher vulnerability than generality, and high niche overlap. The community was composed by a high number of generalist species. To our knowledge this is the first study in which network analyses are conducted with standardized data and including all host and epiphyte species in the community. The analyses suggest that the networks are robust, and that functional redundancy might be probable, two advantageous characteristics in a very fragmented and threatened cloud forest.

Grassland restoration on linear landscape elements – comparing the effects of topsoil removal and topsoil transfer

Artificial linear landscape elements, including roads, pipelines, and drainage channels, are main sources of global habitat fragmentation. Restoration of natural habitats on unused linear landscape elements can increase habitat quality and connectivity without interfering with agricultural or industrial development. Despite that topsoil removal and transfer are widely applied methods in restoration projects, up to our knowledge these were previously not compared in the same study system. To address this knowledge gap, we compared spontaneous vegetation recovery after the elimination of positive (embankments) and negative landscape scars (drainage channels) in lowland alkaline landscapes in South Hungary. The novelty of our study is that we compared the fine-scale and landscape-scale results of both methods. At the fine scale, we monitored the spontaneous vegetation development on the created open surfaces in the first, second and fourth year after restoration in 160 permanent plots per year. For characterizing the habitat changes on the landscape scale, we prepared habitat maps and assigned naturalness scores to each patch before and after the restoration activities. Both restoration methods resulted in a rapid vegetation recovery at the fine scale, progressing toward the reference state. In the topsoil removal treatment, a large part of the soil seed bank was removed; therefore, the colonization of the bare surface was a slower process. Seeds of halophytes, including the endemic and protected Suaeda pannonica, were probably present in the deeper soil layers, and these species became established in the restored surfaces, despite being absent in the surrounding vegetation. For restoring vegetation cover, topsoil transfer was a more rapid option; however, vegetation closure and competition by generalist species and weeds hampered the establishment of target species. The removal of the landscape scars by both methods made the sites accessible for grazing. At the landscape scale, the two methods had different effects: there was a slight increase in the habitat naturalness in the topsoil removal site, and a slight decrease in the topsoil transfer site because of weed encroachment. Spreading an upper layer of nutrient-poor soil with low amounts of weed seeds, direct propagule transfer, and targeted grazing regimes could enhance restoration success.

Influence of wild ungulates on the secondary succession of an Apennine silver fir forest after windthrow

Windstorms are natural factors in vegetation dynamics, but their intensity is increasing and undermines the forest resilience. Post-event interventions depend on forest types and management purposes. To promote mixed stands that are less susceptible to windthrow than monocultures, natural tree regeneration is usually recommended. However, wild ungulates attracted by the increased food supply in the new clearings can influence the secondary succession and slow down vegetation recovery. The impact of ungulate pressure on secondary successions in blowdown areas is still poorly known, especially in Mediterranean areas, which is particularly vulnerable to climate stressors. We investigated this topic using a monospecific silver fir (Abies alba) forest of artificial origin in the Apennines as a model system. The forest was left to natural succession after a severe windthrow in 2015, offering the opportunity to establish an ungulate exclosure experiment to analyse vegetation changes over six years. For the whole plant community, cover and height, α-diversity (species richness, Shannon and evenness indexes), and species composition were recorded yearly, together with tree seedling density, in open and fenced plots at increasing distances from the forest edge. Ecological and functional traits (proportion of light-demanding and forest specialists, endo-/epi-zoochorous species), and life-forms of the community samples were also analysed. Overall, we found that ungulates significantly influenced the dynamic trajectories of secondary succession. The effects on plant cover and diversity were negative and increased with distance from the forest edge. The presence of ungulates favoured generalist species and endozoochorous taxa. However, distance from the forest edge strongly reduced the latter effect. The average density of tree seedlings was overall high (ca. 10,000/ha), but it was strongly reduced by ungulates for three deciduous species and A. alba, the most browsed species. Natural recolonization after windthrow in Apennine pure silver fir stands may favour the formation of mixed, less susceptible forests, but the current ungulate pressure slows down this process, especially in the areas furthest from the forest edge.

Mechanistic conformational and substrate selectivity profiles emerging in the evolution of enzymes via parallel trajectories

Laboratory evolution studies have demonstrated that parallel evolutionary trajectories can lead to genetically distinct enzymes with high activity towards a non-preferred substrate. However, it is unknown whether such enzymes have convergent conformational dynamics and mechanistic features. To address this question, we use as a model the wild-type Homo sapiens kynureninase (HsKYNase), which is of great interest for cancer immunotherapy. Earlier, we isolated HsKYNase_66 through an unusual evolutionary trajectory, having a 410-fold increase in the kcat/KM for kynurenine (KYN) and reverse substrate selectivity relative to HsKYNase. Here, by following a different evolutionary trajectory we generate a genetically distinct variant, HsKYNase_93D9, that exhibits KYN catalytic activity comparable to that of HsKYNase_66, but instead it is a “generalist” that accepts 3’-hydroxykynurenine (OH-KYN) with the same proficiency. Pre-steady-state kinetic analysis reveals that while the evolution of HsKYNase_66 is accompanied by a change in the rate-determining step of the reactions, HsKYNase_93D9 retains the same catalytic mechanism as HsKYNase. HDX-MS shows that the conformational dynamics of the two enzymes are markedly different and distinct from ortholog prokaryotic enzymes with high KYN activity. Our work provides a mechanistic framework for understanding the relationship between evolutionary mechanisms and phenotypic traits of evolved generalist and specialist enzyme species.

Short-term effects of clearing restoration on the relationship of plant and moth communities

Abstract Insects and plants share a close relationship; plants provide feeding opportunities, ecological niches, and shelters for insects, while insects, in turn, facilitate pollination for plants. Management actions might positively or negatively affect insect species richness and/or abundance, in particular, forest practices can significantly influence insect communities. In this study, we investigated the effects on plant and moth communities following the realization of an ecological corridor (composed of 10 clearings) in forest in NW of Italy. Specifically, through plant surveys and moth light traps, we investigated plant and moth communities and their relationship in newly shaped clearings and their surrounding forest. We found that plants responded quickly to clearing formation, presenting differentiated plant communities between xero-thermophile clearings, mesophile clearings and forest. These differences reflected on moth communities as well, allowing to find indicator species for each ecosystem. Structural variables (i.e. openness) and topography (i.e. elevation) were key factors affecting the differentiation of moth communities. On the other hand, plants explained most of the variance in moth communities, so, through plants, we differentiated moth communities into those typical of xero-thermophile clearings, mesophile clearings and forest. In conclusion, forest management significantly affects plant and moth communities. Newly shaped clearings support higher species richness (including specialist species) and abundance than closed canopy forest. To increase species richness and abundance for both plants and moths, we suggest conservation measures that include creating open habitats within forests at medium elevation (650–950 m a.s.l.).

Spatial distribution of cliff plant species in the Balearic Islands under current and projected climatic scenarios

Cliff ecology has been studied for decades, providing information about its high biodiversity values and their vulnerability to climate change. Also, insular ecosystems present biodiversity hotspots with high endemicity, but they are also severely affected by anthropogenic effects. Together, insular cliff communities combine both biodiversity uniqueness and high vulnerability to global change, but few studies have evaluated these particular ecosystems. Our aim was to provide information on the spatial distribution of insular cliff-specific vegetation assessing which environmental and climatic variables contribute to the definition of cliff habitat conditions. Ecological niche modelling for cliff populations in Balearic Islands has been calculated with presences of 20 plant species and climatic and geographical variables using a Random Forest model. The most important climatic variables for the model generation were mean temperature of the driest quarter and precipitation of the coldest quarter. The map obtained showed that mountain ranges from all islands provide highly suitable conditions for rupicolous species. Both the pessimistic and optimistic models showed that the habitat suitability of cliff vegetation in the mountain ranges would decrease, while they are close to zero in lowlands for the period 2021–2040. This study emphasizes the vulnerability of cliff habitats to climate change due to their limited dispersal capacity and distribution and the strict requirements for habitat suitability. From this work, future studies can focus on single-species analysis to evaluate if any cliff specialist species can be at risk of extinction due to climate change.

Unravelling the complexities of biotic homogenization and heterogenization in the British avifauna.

Biotic homogenization is a process whereby species assemblages become more similar through time. The standard way of identifying the process of biotic homogenization is to look for decreases in spatial beta-diversity. However, using a single assemblage-level metric to assess homogenization can mask important changes in the occupancy patterns of individual species. Here, we analysed changes in the spatial beta-diversity patterns (i.e. biotic heterogenization or homogenization) of British bird assemblages within 30 km × 30 km regions between two periods (1988-1991 and 2008-2011). We partitioned the change in spatial beta-diversity into extirpation and colonization-resultant change (i.e. change in spatial beta-diversity within each region resulting from both extirpation and colonization). We used measures of abiotic change in combination with Bayesian modelling to disentangle the drivers of biotic heterogenization and homogenization. We detected both heterogenization and homogenization across the two time periods and three measures of diversity (taxonomic, phylogenetic, and functional). In addition, both extirpation and colonization contributed to the observed changes, with heterogenization mainly driven by extirpation and homogenization by colonization. These assemblage-level changes were primarily due to shifting occupancy patterns of generalist species. Compared to habitat generalists, habitat specialists had significantly (i) higher average contributions to colonization-resultant change (indicating heterogenization within a region due to colonization) and (ii) lower average contributions to extirpation-resultant change (indicating homogenization from extirpation). Generalists showed the opposite pattern. Increased extirpation-resultant homogenization within regions was associated with increased urban land cover and decreased habitat diversity, precipitation, and temperature. Changes in extirpation-resultant heterogenization and colonization-resultant heterogenization were associated with differences in elevation between regions and changes in temperature and land cover. Many of the 'winners' (i.e. species that increased in occupancy) were species that had benefitted from conservation action (e.g. buzzard (Buteo buteo)). The 'losers' (i.e. those that decreased in occupancy) consisted primarily of previously common species, such as cuckoo (Cuculus canorus). Our results show that focusing purely on changes in spatial beta-diversity over time may obscure important information about how changes in the occupancy patterns of individual species contribute to homogenization and heterogenization.

Detection of Viruses in Special Stands of Common Ash Reveals Insights into the Virome of Fraxinus excelsior

Plant diseases are mostly multicausal with several factors influencing the health status of affected hosts. Common ash (Fraxinus excelsior), a significant tree species of European forests, is currently mostly endangered by ash dieback, caused by the invasive fungus Hymenoscyphus fraxineus. However, contributing factors, including pathogenic viruses, are poorly understood. Here, we report the results of a virus screening conducted on selected special stands of F. excelsior. Over three consecutive years, ash trees from different origins were tested, including leaf material from mature seed trees, young trees and ash seedlings from the natural regeneration. Using RT-PCR, we screened for five viruses, including the generalist species ArMV (Nepovirus arabis) and CLRV (Nepovirus avii), as well as newly discovered viruses in ash, including the emaravirus ASaV (Emaravirus fraxini), the idaeovirus PrLBaV (Idaeovirus ligustri), and cytorhabdoviruses. The results revealed a high virus diversity in common ash. An association of ASaV detection with specific leaf symptoms, including shoestring, chlorotic ringspots, and vein yellowing, was documented. An analyses of relevant gene products of cytorhabdoviruses obtained from ashes of different sites revealed sequence diversities and two distinct phylogenetic groups present in ash populations. Signatures of novel viruses from different families have been identified by high-throughput sequencing. Together, our results provide insights into the virus diversity and distribution of viruses in ash and expand our knowledge about the virome of this endangered tree species.

Phenotypic covariation predicts diversification in an adaptive radiation of pupfishes.

Phenotypic covariation among suites of traits may constrain or promote diversification both within and between species, yet few studies have empirically tested this relationship. In this study, we investigate whether phenotypic covariation of craniofacial traits is associated with diversification in an adaptive radiation of pupfishes found only on San Salvador Island, Bahamas (SSI). The radiation includes generalist, durophagous, and lepidophagous species. We compared phenotypic variation and covariation (i.e., the P matrix) between (1) allopatric populations of generalist pupfish from neighboring islands and estuaries in the Caribbean, (2) SSI pupfish allopatric lake populations with only generalist pupfish, and (3) SSI lake populations containing the full radiation in sympatry. Additionally, we examine patterns observed in the P matrices of two independent lab-reared F2 hybrid crosses of the two most morphologically distinct members of the radiation to make inferences about the underlying mechanisms contributing to the variation in craniofacial traits in SSI pupfishes. We found that the P matrix of SSI allopatric generalist populations exhibited higher levels of mean trait correlation, constraints, and integration with simultaneously lower levels of flexibility compared to allopatric generalist populations on other Caribbean islands and sympatric populations of all three species on SSI. We also document that while many craniofacial traits appear to result from additive genetic effects, variation in key traits such as head depth, maxilla length, and lower jaw length may be produced via non-additive genetic mechanisms. Ultimately, this study suggests that differences in phenotypic covariation significantly contribute to producing and maintaining organismal diversity.

Effects of climate change on seed germination may contribute to habitat homogenization in freshwater forested wetlands

Climate changes in temperate regions are expected to result in warmer, shorter winters in temperate latitudes. These changes may have consequences for germination of plant species that require a period of physiological dormancy. The effect of cold duration on seed germination has been investigated in a number of plant taxa, but has not been well studied in wetland and bottomland forest tree species, an ecosystem that is threatened by habitat homogenization. Our work sought to test the role of changing winter temperatures on seed germination in specialist (Nyssa aquatica and Taxodium distichum) and generalist (Acer rubrum and Liquidambar styraciflua) tree species within forested wetlands throughout the eastern U.S. The experiment was conducted in an environmental chamber in Norfolk, VA, USA. Seeds of T. distichum, N. aquatica, A. rubrum, and L. styraciflua were exposed to each of seven pre-germination cold exposure durations (0, 15, 30, 45, 60, 75, and 90 days) and observed for germination for 30 days. Cold stratification duration positively impacted total percent germination in N. aquatica (p < 0.0001) as well as A. rubrum (p = 0.0008) and T. distichum (p = 0.05). Liquidambar styraciflua seeds exhibited more rapid rates of germination with increasing cold exposure duration and greater percent germination compared to the others regardless of cold stratification duration. Our results provide insight into how community dynamics and biodiversity of wetland and bottomland trees may shift with a changing climate. Further, this work emphasizes the importance of understanding the role of plant functional traits in early life stages in community dynamics and has implications for management practices.

Arsenic and metal levels in snake tissues from Lagoa Santa Karst, Brazil.

Concentrations of one metalloid (As) and eight metals (Cd, Cr, Cu, Hg, Mn, Ni, Pb, and Zn) were determined in tissues (muscle, liver, and kidney) of eight snake species (Bothrops neuwiedi, Crotalus durissus, Dipsas mikanii, Epicrates crassus, Helicops modestus, Micrurus carvalhoi, Oxyrhopus guibei, and Oxyrhopus trigeminus) from Lagoa Santa Karst. Except for Cu and Zn, all other analyzed elements were detected in concentrations within the ranges previously reported for snakes inhabiting polluted areas, emphasizing Hg (specific Hg mean concentrations varied from 0.87 to 9.76μgg-1 d.w). The highest mean concentrations of all elements except Zn were found in muscle samples of the false corals O. guibei (means ranged from 2.01 [Pb] to 9.76 [Hg]). The highest Zn mean concentration (13.77μgg-1 d.w) was detected in the kidney of the water snake H. modestus. No significant correlation was found between element concentrations and body size for all species. Significant interorgan differences were observed for As, Cr, Cu, Hg, Mn, Pb, and Zn concentrations in the three tissues in H. modestus. Significant interspecific differences were found in at least one organ for all elements. Significant pairwise differences were found between diet specialist species and between these species and broader diet species, while no significant difference was found between the broader diet species. The bioaccumulation of As and metals in snakes from Lagoa Santa Karst could be associated with natural rock dissolution and erosion processes but also with the wide-scale mining in the region and the increased agriculture and urbanization.

Rapid prey manipulation and bite location preferences in three species of wandering spiders

Predator-prey interactions are the interspecific relationships of greatest interest in ecology. Spiders are among the most diverse and ubiquitous terrestrial predators on the planet. Their large dietary breadth is often linked with the development of specific predatory behaviors and morphological adaptations. However, studies on the predatory behavior of spiders have mostly focused on specialist species, leaving behind the ethological variability occurring in generalist species that allow them to respond to the different prey types. For three species of generalist wandering spiders, we searched images of predation events on the Internet to determine the most common prey. Subsequently, the focal predator species were then used in behavioral experiments. Using high-speed videos, handling patterns for different prey types (spider and cricket) were analyzed. Our results show a notable difference in handling patterns between prey types. We found that the spider prey was often rotated around the axis allowing the predator to bite in the ventral region of the prey and thus avoid a counterattack. Contrary, crickets were arbitrarily rotated. Our work may be an indication that these three species of generalist spiders have a preference for manipulating prey differently with a preference to rotate spiders, allowing them to exploit prey with various defensive mechanisms.

Diversity and dominance in bird assemblages across habitats in the Ñeembucú wetlands complex

AbstractUnderstanding how diversity responds to habitat heterogeneity in a landscape is a central issue for implementing effective conservation plans. In this study, we analyzed how the composition and abundance of neotropical bird assemblages vary among habitats in the Ñeembucú Wetlands Complex, the largest wetland system in Paraguay. Bird surveys were conducted during 1 year within dominant habitats in the landscape: riparian forests, natural grasslands, savannas, and anthropized sites. The Ñeembucú Wetlands Complex showed a high bird richness (209 species) that contrasted with a pattern of dominance by a small set of 16 species that comprised half of the abundance. This set of oligarchic species consists of generalist species that exploited a wide variety of habitats and were well adapted to human disturbance, contributing to an important overlap in the composition of assemblages. However, despite this overall similarity, there is still significant differentiation in bird assemblages, especially between habitats with the most contrasting vegetation physiognomy. Riparian forests and savannas showed higher diversity values than the more structurally homogeneous grasslands. Also, all natural habitats showed, in general, higher diversity values than anthropized sites. Oligarchic species had higher importance in anthropized environments, which also had the most uneven distribution of abundance between species, indicating the dominance by a smaller number of species and the loss of ecological diversity as farmland and urban development increase.Abstract in Spanish is available with online material.