Species-specific Ecological Traits Research Articles

Species-specific ecological traits, phylogeny, and geography underpin vulnerability to population declines for North American birds

Abstract Species declines and extinctions characterize the Anthropocene. Determining species vulnerability to decline, and where and how to mitigate threats, are paramount for effective conservation. We hypothesized that species with shared ecological traits also share threats, and therefore may experience similar population trends. Here, we used a Bayesian modeling framework to test whether phylogeny, geography, and 22 ecological traits predict regional population trends for 380 North American bird species. Groups like blackbirds, warblers, and shorebirds, as well as species occupying Bird Conservation Regions at more extreme latitudes in North America, exhibited negative population trends; whereas groups such as ducks, raptors, and waders, as well as species occupying more inland Bird Conservation Regions, exhibited positive trends. Specifically, we found that in addition to phylogeny and breeding geography, multiple ecological traits contributed to explaining variation in regional population trends for North American birds. Furthermore, we found that regional trends and the relative effects of migration distance, phylogeny, and geography differ between shorebirds, songbirds, and waterbirds. Our work provides evidence that multiple ecological traits correlate with North American bird population trends, but that the individual effects of these ecological traits in predicting population trends often vary between different groups of birds. Moreover, our results reinforce the notion that variation in avian population trends is controlled by more than phylogeny and geography, where closely related species within one region can show unique population trends due to differences in their ecological traits. We recommend that regional conservation plans, i.e. one-size-fits-all plans, be implemented only for bird groups with population trends under strong phylogenetic or geographic controls. We underscore the need to develop species-specific research and management strategies for other groups, like songbirds, that exhibit high variation in their population trends and are influenced by multiple ecological traits.

Population trends of ground-nesting birds indicate increasing environmental impacts from Eastern to Western Europe: different patterns for open-habitat and woodland species

Introduction: Bird populations reflect the influence of major environmental changes, and the analysis of their long-term population trends concerning species-specific ecological traits can provide insight into biologically relevant impacts of such changes. In this respect, nest site is a particularly informative trait because ground-nesting bird species are more prone, in contrast to species nesting above the ground, to the impacts of nest predation which can be linked to various environmental drivers including the intensification of agriculture or woodland management. Here we hypothesize that a) ground-nesting species present negative trends due to environmental pressures mentioned above, b) such declining trends should be more pronounced in Western than in Eastern Europe because, in Western countries, the environmental threats are likely greater, and c) the interaction between nest site and habitat association will point at the habitat types where the presumed drivers most likely operate.Methods: We used population trends from 1980 to 2016 of 332 bird species in 16 European countries to test this hypothesis.Results: We found that the long-term population trends of ground-nesting birds are more negative than the trends of species nesting above the ground indicating the effect of nest predation, and this difference increased from Eastern to Western European countries, probably due to steeply increasing populations of nest predators in the West. However, the effect of longitude interacted with the habitat association being strong in woodland species and weak in open-habitat species.Discussion: This pattern suggests that the increased nest predation pressure in the West is linked to woodlands, probably due to higher abundances of mammalian herbivores that destroy forest ground and shrub layer, and thus leave the nests exposed to predators. In contrast, only a weak longitudinal pattern in open-habitat species indicates that the negative impacts of agricultural intensification are no longer confined to the Western part of the continent. Although nature conservation activities are generally successful in Europe, as indicated by benefits provided by the Natura 2000 network, our results uncovered substantial gaps in delivering such benefits.

The evolutionary origin of avian facial bristles and the likely role of rictal bristles in feeding ecology

Facial bristles are one of the least described feather types and have not yet been systematically studied across phylogenetically diverse avian species. Consequently, little is known about their form, function and evolutionary history. Here we address this knowledge gap by characterising the evolution of facial bristles for the first time. We especially focus on rictal bristle presence and their associations with foraging behaviour, diet and habitat preferences in 1022 avian species, representing 91 families in 29 orders. Results reveal that upper rictal, lower rictal and interramal bristles were likely to be present in the most recent common ancestor of this avian phylogeny, whereas narial bristles were likely to be absent. Rictal bristle presence, length and shape varied both within and between avian orders, families and genera. Rictal bristles were gained or lost multiple times throughout evolution, which suggest that the different morphologies observed within species might not be homologous. Phylogenetic relatedness is also not likely to be the only driver of rictal bristle presence and morphology. Rictal bristle presence and length were associated with species-specific ecological traits, especially nocturnality. Our findings suggest that species foraging in low-light conditions are likely to have longer rictal bristles, and that rictal bristles are likely to have evolved in early birds.

Comparing the genetic diversity and population structure of sister marine snails having contrasting habitat specificity

To grasp the processes of spatial genetic structuring in open and connectable marine environments is the principal study goal in molecular biological studies. Comparative seascape genetics using multiple species are a powerful approach to understand the physical geographic and oceanographic effects on genetic variation. Besides, species-specific ecological traits such as dispersal abilities and habitat specificity are important factors for spatial genetic structuring. We focused on the sister marine snail species Tegula kusairo and T. xanthostigma around the Japanese mainland, which have contrasting habitat specificities for wave strength. Tegula kusairo only inhabits sheltered coastal environments, while T. xanthostigma is found mainly on wave-exposed rocky shores facing the open sea. We estimated their genetic diversity indices and levels of population differentiation based on mtDNA. We found that the genetic diversity of T. kusairo was lower than that of T. xanthostigma, while their level of population genetic differentiation was higher than that of T. xanthostigma. Namely, the species specific to weak wave environments had a higher level of population genetic differentiation than the species specific to strong wave action. Ecological traits linked not only to dispersal abilities but also to habitat specificity can influence genetic variation in a pair of closely related sister species distributed in the same seascape.

Comparing the gut microbiome along the gastrointestinal tract of three sympatric species of wild rodents

Host–microbe interactions within the gastrointestinal tract (GIT) play a pivotal role in shaping host physiology, ecology, and life history. However, these interactions vary across gut regions due to changes in the physical environment or host immune system activity, thereby altering the microbial community. Each animal species may harbor their own unique microbial community due to host species-specific ecological traits such as dietary habits, micro-habitat preferences, and mating behavior as well as physiological traits. While the gut microbiota in wild animals has received much attention over the last decade, most studies comparing closely related species only utilized fecal or colon samples. In this study, we first compared the gut microbial community from the small intestine, cecum, colon, and rectum within three sympatric species of wild rodents (i.e. Apodemus speciosus, A. argenteus, and Myodes rufocanus). We then compared each gut region among host species to determine the effect of both gut region and host species on the gut microbiota. We found that the small intestine harbored a unique microbiome as compared to the lower GIT in all three host species, with the genus Lactobacillus in particular having higher abundance in the small intestine of all three host species. There were clear interspecific differences in the microbiome within all gut regions, although some similarity in alpha diversity and community structure within the small intestine was found. Finally, fecal samples may be appropriate for studying the lower GIT in these species, but not the small intestine.

Fish Specialize Their Metabolic Performance to Maximize Bioenergetic Efficiency in Their Local Environment: Conspecific Comparison Between Two Stocks of Pacific Chub Mackerel (Scomber japonicus)

Species-specific ecological traits in fishes are likely to vary between populations or stocks due to differences in regional oceanic conditions, such as latitudinal temperature. We examined potential intraspecific differences in the swimming performance and metabolism of Pacific chub mackerel (Scomber japonicus) from the Northwest and Northeast Pacific stocks, which are distributed on opposite sides of the North Pacific at similar latitudes, but where the temperature contrast is large. Swimming bioenergetics and metabolic data of Northwest stock mackerel were measured at 14, 18, and 24°C using variable-speed swim-tunnel respirometers, and then the resulting bioenergetic parameters were compared with previous findings from the Northeast stock. At a given size, the maximum sustainable swimming speed (Umax) of the Northwest stock showed no significant difference compared to the Northeast stock at 18 and 24°C, but was lower at 14°C. In addition, the oxygen consumption rate (MO2) of the Northwest stock showed lower mass dependence and different temperature dependence at a given swimming speed than in the Northeast stock. Combined with stock-specific data on growth and experienced temperatures in the wild, these bioenergetic differences indicate that the swimming performance and metabolism of the two stocks are specific to their local environment to maximize bioenergetic efficiency.

Drastic shifts in the Belgian bumblebee community over the last century

Bumblebees are undergoing strong declines in Europe caused by habitat loss and fragmentation, agricultural intensification, and climate change. Long-term records are necessary to estimate population trends precisely and to propose appropriate mitigation strategies. Based on an original database of 173,788 specimens from museum collections, scientific monitoring, and opportunistic citizen data from 1810 to 2016, we compared changes in species richness and area of occupancy of Belgian bumblebee species through three time-periods (1910–1930, 1970–1989, and 1990–2016). We also assessed if the observed trends are related to species-specific ecological traits and spatial scales (local, regional and national). Overall, species richness decreased over the last century in Belgium, but some regions retained relatively species-rich communities. A strong shift in community composition occurred. Three species remained among the “top five” in terms of species occurrence (area of occupancy) between the three time-periods (B. pascuorum, B. lapidarius, and B. pratorum), but several species that were once widespread declined drastically (B. muscorum, B. humilis, B. ruderatus, and B. veteranus), while a few species increased their distribution (e.g. B. hypnorum and B. terrestris). Habitat preferences significantly explained the observed trends, with declining species preferring open habitats and increasing species preferring wooded habitats.

Growth performance and leaf ecophysiological traits in three Aquilaria species in Malaysia

The genus Aquilaria (Thymelaeaceae) is widely used for the production of agarwood, and includes several valuable plantation species in Southeast Asia. To understand appropriate planting conditions, it is necessary to characterize species-specific ecological traits such as photosynthesis and drought tolerance among Aquilaria species. To this end, we measured leaf morphological and photosynthetic traits among three Aquilaria seedlings (A. hirta, A. malaccensis, A. subintegra) in Malaysia. We also monitored changes in growth and survival in a shaded nursery and 7 and 18 months after transfer to open conditions. To avoid transplant stress, the seedlings were kept in polybags. The highest leaf cuticle and epidermis layer ratio, leaf mass per area, and long-term water use efficiency indicated by δ13C were recorded in A. hirta, suggesting that this species had relatively high drought tolerance. By contrast, the high maximum photosynthetic rate and high stomatal conductance observed in A. subintegra explained their high growth rate, although their drought tolerance was the lowest among the studied species. A. malaccensis was considered an intermediate species in terms of photosynthesis and drought tolerance. Interspecific differences in growth and survival were present after transfer to open conditions. A. hirta had the lowest growth rate and highest survival rate (50% survival after 18 months), whereas A. subintegra had the highest growth rate and lowest survival rate (9% survival after 18 months). A. malaccensis was intermediate between the two. In summary, the studied Aquilaria species were susceptible to stress under the open and dry conditions of our study. This includes Aquilaria hirta, the most drought-tolerant species in this group, and A. subintegra, the most vulnerable species to drought, which may require careful management when planted in open conditions.

Stable isotope analyses revealed the influence of foraging habitat on mercury accumulation in tropical coastal marine fish

Bioaccumulation of toxic metal elements including mercury (Hg) can be highly variable in marine fish species. Metal concentration is influenced by various species-specific physiological and ecological traits, including individual diet composition and foraging habitat. The impact of trophic ecology and habitat preference on Hg accumulation was analyzed through total Hg concentration and stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) in the muscle of 132 fish belonging to 23 different species from the Senegalese coast (West Africa), where the marine ecosystem is submitted to nutrient inputs from various sources such as upwelling or rivers. Species-specific ecological traits were first investigated and results showed that vertical (i.e. water column distribution) and horizontal habitat (i.e. distance from the coast) led to differential Hg accumulation among species. Coastal and demersal fish were more contaminated than offshore and pelagic species. Individual characteristics therefore revealed an increase of Hg concentration in muscle that paralleled trophic level for some locations. Considering all individuals, the main carbon source was significantly correlated with Hg concentration, again revealing a higher accumulation for fish foraging in nearshore and benthic habitats. The large intraspecific variability observed in stable isotope signatures highlights the need to conduct ecotoxicological studies at the individual level to ensure a thorough understanding of mechanisms driving metal accumulation in marine fish. For individuals from a same species and site, Hg variation was mainly explained by fish length, in accordance with the bioaccumulation of Hg over time. Finally, Hg concentrations in fish muscle are discussed regarding their human health impact. No individual exceeded the current maximum acceptable limit for seafood consumption set by both the European Union and the Food and Agriculture Organization of the United Nations. However, overconsumption of some coastal demersal species analyzed here could be of concern regarding human exposure to mercury.

Contrasted patterns of genetic differentiation across eight bird species in the Lesser Antilles.

Archipelagoes are considered as "natural laboratories" for studying processes that shape the distribution of diversity. The Lesser Antilles provide a favorable geographical context for divergence to occur. However, although morphological subspecies have been described across this archipelago in numerous avian species, the potential for the Lesser Antilles in driving intra-specific genetic divergence in highly mobile organisms such as birds remains understudied. Here, we assessed level of intra-specific genetic diversity and differentiation between three islands of the Lesser Antilles (Guadeloupe, Dominica and Martinique) using a multi-species approach on eight bird species. For each species, we built a set of microsatellite markers from cross-species amplifications. Significant patterns of inter-island and/or within-island genetic differentiation were detected in all species. However, levels of intra-specific genetic differentiation among the eight bird species were not always consistent with the boundaries of subspecies previously described in the sampled islands. These results suggest different histories of colonization/expansion and/or different species-specific ecological traits affecting gene flow, advocating for multi-species studies of historical and contemporary factors shaping the distribution of diversity on islands.

The Lower Mekong: an insurmountable barrier to amphibians in southern Indochina?

Geographical information system (GIS)-based cluster analyses and comparative ecological approaches were applied to unravel the hitherto controversially discussed role of the Mekong River as a biogeographical barrier to the amphibian fauna in Indochina. Referring to the unique and independent history of the Lower Mekong, south of the Lao-Cambodian border, this approach focused on the amphibians of southern Indochina and adjacent parts of eastern Thailand. To date, 131 amphibian species have been recorded from this region. In concordance with previous studies, our GIS-based analyses revealed that the amphibian fauna of the Cardamom Mountains, west of the Mekong, possessed no closer affinity to the herpetofauna of the Southern Annamites. In addition, a statistical comparison of ecological characters showed an occurrence of ecological differentiation among amphibians across the Lower Mekong. Our results suggest that the Lower Mekong serves as, or at least coincides with, a biogeographical barrier in southern Indochina. Here, we discuss this hypothesis, together with selected species spatial distribution patterns, their species-specific ecological traits and the palaeogeographical background of the region.(c) 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114, 905-914.

What species-specific traits make a bird a better surrogate of native species richness? A test with insular avifauna

Identification of species-specific traits that make a species a better surrogate of biodiversity is a need in order to implement successful conservation programmes in the face of limited data and resources. This study analyzes the relationship between the abundance of different surrogate species and species richness for terrestrial native avifauna of autochthonous steppe and semiarid environments in Fuerteventura Island (Spain) at different spatial grains, and explores which species-specific ecological traits (body mass, ecological density, habitat breadth, coverage of urban and agricultural environments) and conservation features (endemicity, conservation status) make a species more efficient as a surrogate. Results indicate that abundance of those surrogate species which are typically targeted by local conservation managers (according to their rarity and increase public awareness) proves to be a poor predictor of three different measures of species richness of the native terrestrial avifauna of Fuerteventura at all spatial resolutions. Nonetheless, some species were found to perform better than others according to partial least squares regression analyses applied to relate species-specific ecological traits and conservation features with correlation coefficients between abundance of each bird species and total bird richness. The best surrogates for global bird species richness are those smaller birds of medium–high abundances, broad habitat preferences, less threatened status, and with a high degree of endemicity. No scale-dependency was observed in the surrogacy power of species. Conservation planners in island scenarios should use a selection of bird species with these characteristics to identify conservation target areas in order to maximize the efficiency of surrogacy approaches.

Long-term changes in spatial patterns of emergent vegetation in a Mediterranean floodplain: natural versus anthropogenic constraints

This study describes the long-term changes of spatial patterns of cut-sedge (Cladium mariscus) and common reed (Phragmites australis) in the Spanish floodplain wetland Las Tablas de Daimiel. Using seven sets of aerial photographs, we determined changes in their spatial patterns (size of patches) between 1945 and 2001 that resulted from combinations of natural change and anthropogenic stress (irrigated agriculture, waste water discharge, fire, ploughing). Our approach consisted in using 1 ha cells as units of spatial resolution in principal coordinates of neighbour matrices and spatial correlograms to assess the spatial scale of interest and spatial patterns at (1) the whole wetland and (2) two areas of the wetland with locally contrasting biophysical settings and anthropogenic stress history. Results showed that vegetation spatial patterns were influenced by natural variability until the 1970s. Thereafter, anthropogenic perturbation became the main driver of vegetation change, especially in the lower part of the wetland where local impacts were stronger. Natural variability did not fragment cut-sedge patches, and the effects of biological traits were less important for its spatial pattern. By contrast, man-made change resulted in a marked cut-sedge cover decrease and patch fragmentation, and the importance of its biological traits on spatial patterns increased. The trends of reed spatial patterns were generally opposite to, but not as clear as those for, cut-sedge. The trends of spatial patterns were especially evident at very broad (3,500–10,000 m) and broad (1,000–3,400 m) spatial scales. Competition for space and abiotic factors (water quality and water depth) were not strong predictors of cover variability at the 1-ha scale, particularly in the lower area of the wetland. This suggests that other environmental variables need to be considered in spatially explicit modelling of vegetation spatial patterns in wetlands. Consideration of spatial hierarchies and species-specific ecological traits is paramount to the conservation of degraded wetlands.