Ratio changes in blood-feeding and voltinism in black flies (Diptera: Simuliidae) over a latitudinal gradient in North America north of Mexico.

We explored how the ratio of blood-feeding behaviour-nonfeeding, bird feeding (ornithophily) and mammal feeding (mammalophily)-and voltinism (univoltine and multivoltine) vary over a latitudinal gradient from Alaska to Florida. These two fixed species traits were divided into five mutually exclusive combinations of trait states-nonfeeding/univoltine, ornithophilic/univoltine, mammalophilic/univoltine, ornithophilic/multivoltine and mammalophilic/multivoltine-within each of three datasets (north, east and west). We found a significant association between location (north, east and west) and trait state, which was driven by the large percentage of nonfeeding females in the north. When this trait state was removed, no significant differences were found for the remaining trait states and locations. Although the distribution of trait states did not differ between east and west datasets, the distribution with relation to 1° changes in latitude within each of these datasets showed distinct differences. In the east, both ornithophilic/univoltine and mammalophilic/univoltine species significantly increased with latitude, in proportion to the total species present. In contrast, the proportion of mammalophilic/multivoltine species decreased as latitude increased. Ornithophilic/multivoltine species in the east and the trait states in the west did not show any significant relationship to latitude.

Impacts of urban and industrial pollution on functional traits of benthic macroinvertebrates: Are some traits advantageous for survival?

Urbanization and industrialization produce substantial changes in biodiversity and in the functionality of ecosystems. However, little is known about how anthropic pressures might drive these changes and about their functional consequences. We aimed to determine the responses of macroinvertebrate biological traits to urban and industrial pollution and assess the impacts of these disturbances on the functional diversity of these assemblages. We sampled benthic macroinvertebrates in 27 sites of four basins with different urban disturbance gradients (rural, peri-urban, and urban-industrial), among them the Matanza-Riachuelo River, one of the most polluted basins in the world. We classified macroinvertebrates into 11 traits and 56 categories. Then, we performed an RLQ analysis and computed functional richness, evenness, divergence and Rao diversity indexes for each site and community weighted means for each trait category. The urban and industrial sites (mainly low and middle Matanza-Riachuelo River Basin) showed high concentrations of ammonium, SRP, conductivity, COD, BOD, and organic matter, as well as the lowest values of DO. The functional richness and Rao index of these sites were significantly lower than that of the other sites. Macroinvertebrate traits associated with urban and industrial sites were aerial respiration (spiracles), forms of resistance (eggs or statoblast), cylindrical body shape, oviparity, feeding on microinvertebrates, and full water swimmers. These traits potentially enabled tolerant species persistence at polluted sites while gills, grazers, and crawlers were sensitive to these disturbances. Urban and industrial activities influence biological traits, producing the disappearance or dominance of certain traits in macroinvertebrate assemblages. As a consequence, extreme pollution caused predictable trait-based community changes resulting in reduced functional diversity, and potentially altered the ecosystem function.

Genetic variation in neotropical butterflies is associated with sampling scale, species distributions, and historical forest dynamics.

Previous studies of butterfly diversification in the Neotropics have focused on Amazonia and the tropical Andes, while southern regions of the continent have received little attention. To address the gap in knowledge about the Lepidoptera of temperate South America, we analysed over 3000 specimens representing nearly 500 species from Argentina for a segment of the mitochondrial cytochrome c oxidase subunit I (COI) gene. Representing 42% of the country's butterfly fauna, collections targeted species from the Atlantic and Andean forests, and biodiversity hotspots that were previously connected but are now isolated. We assessed COI effectiveness for species discrimination and identification and how its performance was affected by geographic distances and taxon coverage. COI data also allowed to study patterns of genetic variation across Argentina, particularly between populations in the Atlantic and Andean forests. Our results show that COI discriminates species well, but that identification success is reduced on average by ~20% as spatial and taxonomic coverage rises. We also found that levels of genetic variation are associated with species' spatial distribution type, a pattern which might reflect differences in their dispersal and colonization abilities. In particular, intraspecific distance between populations in the Atlantic and Andean forests was significantly higher in species with disjunct distributions than in those with a continuous range. All splits between lineages in these forests dated to the Pleistocene, but divergence dates varied considerably, suggesting that historical connections between the Atlantic and Andean forests have differentially affected their shared butterfly fauna. Our study supports the fact that large-scale assessments of mitochondrial DNA variation are a powerful tool for evolutionary studies.

Leaf turgor loss point shapes local and regional distributions of evergreen but not deciduous tropical trees.

The effects of climate change on tropical forests will depend on how diverse tropical tree species respond to drought. Current distributions of evergreen and deciduous tree species across local and regional moisture gradients reflect their ability to tolerate drought stress, and might be explained by functional traits. We measured leaf water potential at turgor loss (i.e. 'wilting point'; πtlp ), wood density (WD) and leaf mass per area (LMA) on 50 of the most abundant tree species in central Panama. We then tested their ability to explain distributions of evergreen and deciduous species within a 50 ha plot on Barro Colorado Island and across a 70 km rainfall gradient spanning the Isthmus of Panama. Among evergreen trees, species with lower πtlp were associated with drier habitats, with πtlp explaining 28% and 32% of habitat association on local and regional scales, respectively, greatly exceeding the predictive power of WD and LMA. In contrast, πtlp did not predict habitat associations among deciduous species. Across spatial scales, πtlp is a useful indicator of habitat preference for tropical tree species that retain their leaves during periods of water stress, and holds the potential to predict vegetation responses to climate change.

Searching for synthetic mechanisms on how biological traits mediate species responses to climate change / Em busca de mecanismos sintéticos sobre como os atributos biológicos mediam as respostas das espécies às mudanças climáticas

Abstract: Climate change will likely be the most significant challenge faced by species in this century, and species' ability to cope with climate change depends on their life history and ecological and evolutionary traits. Understanding how these traits mediate species' responses is beneficial for identifying more vulnerable species or prone to extinction risk. Here, we carried out a literature review describing how four traits commonly used in vulnerability assessments (i.e. clutch size, diet breadth, dispersal ability, and climatic tolerance) may determine species vulnerability. We also portray the possible mechanisms that explain how these traits govern species responses to climate change. The literature suggests different mechanisms operating for the evaluated traits. The mechanism of response to climate change differs between species inhabiting tropical and temperate regions: while species from the temperate areas may respond positively to temperature rise, tropical species may be severely affected. Since ectotherms depend on environment temperature, they are more sensitive and present different response mechanisms from endotherms.

Resumo: A mudança climática provavelmente será o maior desafio enfrentado pelas espécies neste século e a capacidade das espécies em lidar com a mudança climática depende de seus próprios atributos de história de vida, ecológicos e evolutivos. Entender como esses atributos mediam as respostas das espécies é extremamente útil para identificar espécies que são mais vulneráveis ou sujeitas ao risco de extinção. Aqui, realizamos uma revisão da literatura com foco na descrição de como quatro atributos comumente usados em avaliações de vulnerabilidade (tamanho da ninhada, amplitude da dieta, capacidade de dispersão e tolerância climática) podem realmente determinar a vulnerabilidade das espécies. Também retratamos os possíveis mecanismos que explicam como esses atributos governam as respostas das espécies à mudança climática. A literatura sugere diferentes mecanismos operando para os atributos avaliados. O mecanismo de resposta à mudança climática difere entre as espécies que habitam as regiões tropicais e temperadas: enquanto as espécies das regiões temperadas podem responder positivamente ao aumento da temperatura, as espécies tropicais podem ser severamente afetadas. Como os ectotérmicos dependem da temperatura ambiente, eles são mais sensíveis e apresentam mecanismos de resposta diferentes dos endotérmicos.

Biogeographic context dependence of trophic cascade strength in bromeliad food webs.

Ecosystem functions and the biomass of lower trophic levels are frequently controlled by predators. The strength of top-down control in these trophic cascades can be affected by the identity and diversity of predators, prey, and resources, as well as environmental conditions such as temperature, moisture, and nutrient loading, which can all impact interaction strength between trophic levels. Few studies have been able to replicate a complete community over a large geographic area to compare the full trophic cascade in a manipulative experiment. Here, we identify geographic dependency in trophic cascade strength, and the driving factors and specific mechanisms behind it, by combining geographically replicated experiments with a novel approach of community analogues of common garden and transplant experiments. We studied a predator-detritivore-detritus food web in bromeliads in Puerto Rico, Costa Rica, and Brazil. We found that interaction strengths between resources, consumers, and predators were strongly site-specific, but the exact mechanism differed between trophic levels. Large bodied predators created strong interaction strengths between predator and consumer trophic levels, reducing consumer abundance regardless of the geographic location, whereas small-bodied predators created weak interactions with no impact on consumer abundances in any site. In contrast, the interaction strength between consumers and resources varied among sites, depending on the dominant species of leaf detritus. More labile leaf species in Costa Rica created a strong consumer-resource interaction and therefore strong trophic cascade, whereas tougher leaf species in Brazil created a weak consumer-resource interaction, and an overall weaker trophic cascade. Our study highlights the importance of replicating experiments over geographic scales to understand general patterns of ecological processes.

The Saturniidae of Barro Colorado Island, Panama: A model taxon for studying the long-term effects of climate change?

We have little knowledge of the response of invertebrate assemblages to climate change in tropical ecosystems, and few studies have compiled long-term data on invertebrates from tropical rainforests. We provide an updated list of the 72 species of Saturniidae moths collected on Barro Colorado Island (BCI), Panama, during the period 1958-2016. This list will serve as baseline data for assessing long-term changes of saturniids on BCI in the future, as 81% of the species can be identified by their unique DNA Barcode Index Number, including four cryptic species not yet formally described. A local species pool of 60 + species breeding on BCI appears plausible, but more cryptic species may be discovered in the future. We use monitoring data obtained by light trapping to analyze recent population trends on BCI for saturniid species that were relatively common during 2009-2016, a period representing >30 saturniid generations. The abundances of 11 species, of 14 tested, could be fitted to significant time-series models. While the direction of change in abundance was uncertain for most species, two species showed a significant increase over time, and forecast models also suggested continuing increases for most species during 2017-2018, as compared to the 2009 base year. Peaks in saturniid abundance were most conspicuous during El Niño and La Niña years. In addition to a species-specific approach, we propose a reproducible functional classification based on five functional traits to analyze the responses of species sharing similar functional attributes in a fluctuating climate. Our results suggest that the abundances of larger body-size species with good dispersal abilities may increase concomitantly with rising air temperature in the future, because short-lived adults may allocate less time to increasing body temperature for flight, leaving more time available for searching for mating partners or suitable oviposition sites.

Do species' strategies and type of stress predict net positive effects in an arid ecosystem?

A proposed refinement to the stress-gradient hypothesis requires consideration of the strategies of the interacting species and the characteristics of the stress factors. While the strength and direction of these interactions can be predicted for different ecosystems, this idea remains largely untested in the field. We performed a manipulative field experiment complemented with a descriptive study to test the predictions in a natural setting that represents the extreme end of a precipitation gradient. There, wind driven desiccation and water availability are the main stressors (non-resource and resource-based stresses, respectively). We evaluated the interaction between the shrub and grasses that are dominant in the Patagonian steppe. The species had differences in morpho-functional traits and drought tolerance that fit into the C-S axis of Grime's strategies. We experimentally separated root zones to limit direct competition for soil moisture and reduce the resource-based stress on grasses. We also manipulated the distance to shrubs to evaluate non-resource stress amelioration by canopies (e.g., sun and wind) on grasses. Finally, we evaluated the distribution of naturally established C and S grasses in the neighborhood of C and S shrubs to infer process-pattern relationships. Our growth data coincide to a large degree to the predictions. We found positive effects on the growth of beneficiaries when stress was non-resource based and when strategies differed (i.e., Cshrub -Sgrass and Sshrub -Cgrass ). We also found strong negative effects when the abiotic stress was driven by water, particularly on C grasses. Additionally, shrubs only increased the survival of grasses when strategies differed (i.e., Cshrub -Sgrass and Sshrub -Cgrass ). Our manipulative and descriptive study supported previous results that showed that stress-tolerant species are important for the persistence of competitive species at high stress. While the applicability and generality of these predictions remains to be tested with more field experiments, some ecological factors, such as stress types and species traits, can explain much of the variation in how dominant shrubs and grasses interact in this extreme arid environment. Moreover, this framework could be extended to specifically test the importance of facilitation under different levels of stress.