There is a growing interest in the physiology underpinning heat tolerance of ectotherms and their responses to the ongoing rise in temperature. However, there is no consensus about the underlying physiological mechanisms. According to "the maintain aerobic scope and regulate oxygen supply" hypothesis, responses to warming at different organizational levels contribute to the ability to safeguard energy metabolism via aerobic pathways. At the cellular level, a decrease in cell size increases the capacity for the uptake of resources (e.g., food and oxygen), but the maintenance of electrochemical gradients across cellular membranes implies greater energetic costs in small cells. In this study, we investigated how different rearing temperatures affected cell size and heat tolerance in the fruit fly Drosophila melanogaster. We tested the hypothesis that smaller-celled flies are more tolerant to acute, intense heat stress whereas larger-celled flies are more tolerant to chronic, mild heat stress. We used the thermal tolerance landscape framework, which incorporates the intensity and duration of thermal challenge. Rearing temperatures strongly affected both cell size and survival times. We found different effects of developmental plasticity on tolerance to either chronic or acute heat stress. Warm-reared flies had both smaller cells and exhibited higher survival times under acute, intense heat stress when compared to cold-reared flies. However, under chronic, mild heat stress, the situation was reversed and cold-reared flies, consisting of larger cells, showed better survival. These differences in heat tolerance could have resulted from direct effects of rearing temperature or they may be mediated by the correlated changes in cell size. Notably, our results are consistent with the idea that a smaller cell size may confer tolerance to acute temperatures via enhanced oxygen supply, while a larger cell may confer greater tolerance to chronic and less intense heat stress via more efficient use of resources.
Variation in environmental conditions during development can lead to changes in life-history traits with long-lasting effects. Here, we study how variation in temperature and host plant (i.e. the consequences of potential maternal oviposition choices) affects a suite of life-history traits in pre-diapause larvae of the Glanville fritillary butterfly. We focus on offspring survival, larval growth rates and relative fat reserves, and pay specific attention to intraspecific variation in the responses (G × E × E). Globally, thermal performance and survival curves varied between diets of two host plants, suggesting that host modifies the temperature impact, or vice versa. Additionally, we show that the relative fat content has a host-dependent, discontinuous response to developmental temperature. This implies that a potential switch in resource allocation, from more investment in growth at lower temperatures to storage at higher temperatures, is dependent on the larval diet. Interestingly, a large proportion of the variance in larval performance is explained by differences among families, or interactions with this variable. Finally, we demonstrate that these family-specific responses to the host plant remain largely consistent across thermal environments. Together, the results of our study underscore the importance of paying attention to intraspecific trait variation in the field of evolutionary ecology.
As a result of concerted efforts of the community of Annonaceae taxonomists, increasingly detailed knowledge of the diversity of the Neotropical genera has been documented. With the exception of just two large genera, Annona and Xylopia, all Neotropical Annonaceae have been revised within the last 25 years. Subsequent to these publications, many new specimens have been collected and sent to us in Leiden for identification. These included a number that, despite the advanced state of taxonomic knowledge, proved to represent rarely collected, undescribed species. Here we describe 12 new species of Annona, Guatteria, Klarobelia, Tetrameranthus, and Xylopia. These species serve to illustrate the still underestimated diversity of the Neotropical flora, even in well studied plant groups like Annonaceae.
Despite its importance, biodiversity is declining rapidly. To adequately prioritise conservation efforts, we need to know how threatened species actually are. The International Union for the Conservation of Nature (IUCN) Red List is the most widely recognised tool for assessing extinction risk. Unfortunately, many lesser-known species are not yet represented, such as those that are rarely collected or are in speciesrich taxon groups. This is potentially due to low data availability, although Red List assessments can still be made with little data. We present a method to rapidly assess the conservation status of species that have low data availability, which will speed up the inclusion of species from large groups into the IUCN Red List. Summary• The International Union for the Conservation of Nature (IUCN) Red List is the most widely recognised tool to assess the extinction risk of species. For it to be effective in directing conservation effort, it is important that as many species as possible are represented, but many are unfortunately not. A lack of data is often the main reason for this, especially for lesser-studied species. However, this does not mean assessments cannot be made.• We examine the use of georeferenced herbarium data in combination with species distribution modelling for assessing plants on the IUCN Red List, with Guatteria (Annonaceae), a genus of Neotropical trees, as a case study. We focus on differences between preliminary and officially published assessments, show the final conservation status of all Guatteria species and provide a roadmap for compiling Red List assessments for species-rich plant groups in the future.• We found that species-distribution models aid in compiling Red List assessments, especially for taxa that lack data, but expert opinion remains an important source of information. Half of Guatteria species (48.0%) are Least Concern, and 13.1% of species are near threatened or threatened. The remaining species are Data Deficient or Not Evaluated. Most of our preliminary assessments remained unchanged upon review and publication on the IUCN Red List.
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