Recent theory suggests that global warming may be catastrophic for tropical ectotherms. Although most studies addressing temperature effects in ectotherms utilize constant temperatures, Jensen's ...inequality and thermal stress considerations predict that this approach will underestimate warming effects on species experiencing daily temperature fluctuations in nature. Here, we tested this prediction in a neotropical pseudoscorpion. Nymphs were reared in control and high-temperature treatments under a constant daily temperature regime, and results compared to a companion fluctuating-temperature study. At constant temperature, pseudoscorpions outperformed their fluctuating-temperature counterparts. Individuals were larger, developed faster, and males produced more sperm, and females more embryos. The greatest impact of temperature regime involved short-term, adult exposure, with constant temperature mitigating high-temperature effects on reproductive traits. Our findings demonstrate the importance of realistic temperature regimes in climate warming studies, and suggest that exploitation of microhabitats that dampen temperature oscillations may be critical in avoiding extinction as tropical climates warm.
1. Ecologists often make predictions about community richness and diversity using climate variables that include seasonal precipitation totals and mean daily temperatures. While means and totals can ...be effective predictors to a certain extent, the complexities of faunal–climate relationships might be over‐simplified through the use of coarse‐grained variables. 2. The goal of this study was to investigate less commonly studied climate variables, including indices of intra‐annual variation in the timing and intensity of precipitation events that might be used to predict butterfly richness across an elevational gradient. Data from a long‐term, single‐observer dataset at four sites in California were examined with Bayesian model averaging and structural equation modelling. Species‐specific responses to climate were compared with community responses at each site. 3. At lower elevations, it was found that the relative importance of climate variables shifted towards temporal patterns of precipitation, including the timing of the first storm event and the annual number of precipitation events. Heterogeneity among sites was apparent in the importance of specific weather variables, and temporal trends (across years) were detected for a small number of variables. Species‐specific results paralleled those obtained from analysis of species richness, thus suggesting a commonality of response to climate across site‐specific assemblages. 4. Models were improved by inclusion of the Pacific Decadal Oscillation and El Niño‐Southern Oscillation indices, indicating that regional variables can profitably be included in faunal–climate relationship analyses. These results emphasise the need for researchers to examine climate variables beyond the most readily summarised means and totals.
Recent theory suggests that tropical terrestrial arthropods are at significant risk from climate warming. Metabolic rate in such ectothermic species increases exponentially with environmental ...temperature, and a small temperature increase in a hot environment can therefore have a greater physiological impact than a large temperature increase in a cool environment. In two recent studies of the neotropical pseudoscorpion,
, simulated climate warming significantly decreased survival, body size and level of sexual dimorphism. However, these effects were minor compared with catastrophic consequences for male fertility and female fecundity, identifying reproduction as the life stage most vulnerable to climate warming. Here, we examine the effects of chronic high-temperature exposure on epigenetic regulation in
in the context of naturally occurring variation in mitochondrial DNA. Epigenetic mechanisms, including DNA methylation, histone modifications and small non-coding RNA (sncRNA) expression, are particularly sensitive to environmental factors such as temperature, which can induce changes in epigenetic states and phenotypes that may be heritable across generations. Our results indicate that exposure of male pseudoscorpions to elevated temperature significantly altered the expression of >60 sncRNAs in testicular tissue, specifically microRNAs and piwi-interacting RNAs. Mitochondrial haplogroup was also a significant factor influencing both sncRNAs and mitochondrial gene expression. These findings demonstrate that chronic heat stress causes changes in epigenetic profiles that may account for reproductive dysfunction in
males. Moreover, through its effects on epigenetic regulation, mitochondrial DNA polymorphism may provide the potential for an adaptive evolutionary response to climate warming.
When both sexes mate with multiple partners, theory predicts that males should adjust their investment in ejaculates in response to the risk and/or intensity of sperm competition. Here, we ...demonstrate that, in the harlequin beetle riding pseudoscorpion, Cordylochernes scorpioides, males use cues deposited on females by previous males to distinguish between virgin, once-mated, and multiply-mated females and adjust sperm allocation accordingly. Sperm number declined in direct proportion to the number of previous males, with virgin females receiving nearly three times more sperm than females exposed to three previous males. Given the lack of first-male sperm precedence in C. scorpioides, this pattern is not consistent with current sperm competition models and appears best explained by a significant risk of wasting ejaculates on deceitful, mated females. In C. scorpioides, males transfer sperm indirectly to females via a stalked spermatophore deposited on the substrate. Mated females often feign sexual receptivity and cooperate throughout mating, only to reject the sperm packet produced by the male. While indirect sperm transfer facilitates a high level of female deceit and control, females of many species are able to influence the number and fate of sperm transferred during copulation and are likely to conceal their sexual unreceptivity to minimize male retaliation. If males cannot accurately assess female receptivity, increased risk of sperm rejection by mated females could outweigh the risk of sperm competition and favor greater sperm allocation to virgin females.
Maternal inheritance of mitochondria creates a sex-specific selective sieve with implications for male longevity, disease susceptibility and infertility. Because males are an evolutionary dead end ...for mitochondria, mitochondrial mutations that are harmful or beneficial to males but not females cannot respond directly to selection. Although the importance of this male/female asymmetry in evolutionary response depends on the extent to which mitochondrial mutations exert antagonistic effects on male and female fitness, few studies have documented sex-specific selection acting on mitochondria. Here, we exploited the discovery of two highly divergent mitochondrial haplogroups (A and B2) in central Panamanian populations of the pseudoscorpion Cordylochemes scorpioides. Next-generation sequencing and phylogenetic analyses suggest that selection on the ND4 and ND4L mitochondrial genes may partially explain sexually antagonistic mitochondrial effects on reproduction. Males carrying the rare B2 mitochondrial haplogroup enjoy a marked advantage in sperm competition, but B2 females are significantly less sexually receptive at second mating than A females. This reduced propensity for polyandry is likely to significantly reduce female lifetime reproductive success, thereby limiting the spread of the male beneficial B2 haplogroup. Our findings suggest that maternal inheritance of mitochondria and sexually antagonistic selection can constrain male adaptation and sexual selection in nature.
Aim The extent to which cryptic species contribute to neotropical diversity remains inadequately investigated. Based on its highly distinctive morphology, the giant harlequin beetle, Acrocinus ...longimanus, is currently described as a single species, ranging from southern Mexico to northern Argentina. However, the discovery of cryptic species in Cordylochernes scorpioides, a pseudoscorpion with obligate dependence on the harlequin beetle for dispersal, strongly suggests the existence of barriers to gene flow in A. longimanus. The aim of this study was therefore to determine whether levels of DNA divergence between geographical populations provided evidence of genetically distinct lineages in the harlequin beetle. Location Trinidad and Panamá. Methods Sequencing of 1245 bp of the mitochondrial cytochrome oxidase I (COI) gene of A. longimanus from seven locations in Trinidad and Panamá. Results Mitochondrial haplotype diversity in the harlequin beetle shows limited evidence of geographical structuring, with a maximum sequence divergence between populations of only 1.29%. This is an order of magnitude less than the level of COI divergence between harlequin beetle riding pseudoscorpions from the same geographical locations. Main conclusions The molecular data on populations from northern South America and Panamá are consistent with the current, morphologically based classification of A. longimanus as a single, pan-neotropical species. In addition, the relatively low level of population divergence detected in this study indicates that speciation in the hitchhiking pseudoscorpion has occurred in the absence of significant barriers to gene flow in its beetle host. It is proposed that, in the harlequin beetle, the phylogenetic signal of colonization and vicariance associated with the formation of the Isthmus of Panamá has been obscured, although not fully erased, by historical and contemporary gene flow.
Human immunoglobulin prepared for intravenous administration (IGIV) has a number of important uses in the treatment of disease. Some of these are in diseases for which acceptable treatment ...alternatives do not exist. In this review we have evaluated the evidence underlying a wide variety of IGIV uses and make specific recommendations on the basis of these data. Given the potential risks and inherent scarcity of IGIV, careful consideration of the indications for and administration of IGIV is warranted.
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