Socioecological and phylogenetic patterns in the chemical signals of strepsirrhine primates

Our understanding of chemical signals in mammals derives principally from studies in which researchers examine signal structure or function within a single species. Despite the unique information to be gained from applying comparable methods across multiple species, comparative studies of chemical signals are extremely limited. Here, we review the available literature on the evolution of chemosignals in male and female strepsirrhine primates (galagos, lorises and lemurs), all of which rely heavily on chemical communication. We draw from a few case studies, but focus our review on two comparative studies. In one, researchers examined the volatile chemical composition of urinary signals across 12 species representing most families within Strepsirrhini, including six 'urine-marking' species and six glandular or 'nonurine-marking' species. In the other, researchers examined the volatile chemical composition of glandular signals in eight Eulemur species differing in social or dominance structure. We highlight five findings. (1) Regardless of the scent source, chemical profiles differ substantially between species, providing reliable species 'scent signatures'. None the less, (2) urine markers express more compounds and have more distinguishable species scent signatures in their urine than do nonurine markers, suggesting specialization of function. Within Eulemur (3) chemical richness is greater in multimale-multifemale species than in pair-bonded species. Moreover, (4) whereas chemical richness of male signals is greater in sexually codominant species, chemical richness of female signals is greater in female-dominant species. Together, the findings from both comparative studies, coupled with case studies, suggest that signal richness is linked to some aspect of the focal species' socioecology. Lastly, (5) regardless of the scent source, strepsirrhine chemosignals evolve gradually over time, but at fast rates and homogeneously within different lineages. Comparative studies reveal patterns that cannot be detected from the single-species approach and are therefore critical for providing new insight into the function and evolution of olfactory signals

Tardigrade Abundance in Relation to Urbanisation and Highly Anthropogenic Substrates

Animals colonising urban environments are exposed to a series of novel stressors and ecological challenges, which can result in adaptations to alternative urban niches. Tardigrades are cosmopolitan invertebrates present in all types of ecosystems, including urban environments; and they can survive under extreme conditions, including periods of desiccation, thus allowing them to colonise novel harsh habitats. Tardigrades are thus a promising model to investigate the challenges and opportunities encountered by urban colonisers. Our aims were 1, to determine if tardigrade abundance in natural substrates (moss, lichen and leaf litter) differs between rural and urban sites and 2, to assess if tardigrades have successfully colonised urban substrates that are highly anthropogenic (road sediment, and material accumulated under cars and in wall crevices). Among natural substrates, we found fewer tardigrades in Cork city than in rural sites. However, in urban sites we found no differences between the number of tardigrades present in natural and anthropogenic substrates. In fact, the highest tardigrade abundances in urban samples were found in abiotic material accumulated in wall crevices. We conclude that even though urbanisation may restrict tardigrade abundance, this group of organisms can successfully colonise alternative urban substrates. More research is needed on the ability of tardigrades and other taxa to inhabit highly unusual and disturbed urban substrates effectively, and the adaptations that may take place when animals colonise such substrates

Changes in the Home Range Sizes of Terrestrial Vertebrates in Response to Urban Disturbance: A Meta-Analysis

The unprecedented growth rate in human population and the increasing movement of people to urban areas is causing a rapid increase in urbanisation globally. Urban environments may restrict or affect the behaviour of many animal species. Importantly, urban populations may change their spatial movement, particularly decreasing their home ranges in response to habitat fragmentation, the presence of landscape barriers and the availability and density of resources. Several species specific studies suggest that urban animals decrease their home ranges compared with their non-urban counterparts; however, it remained unclear whether this pattern is widespread across taxa or is instead restricted to specific taxonomic groups. Consequently, we conducted a meta-analysis, collecting 41 sets of data comparing home ranges in both natural and urban environments in 32 species of reptiles, birds and mammals. We calculated effect sizes as the difference in animal home range sizes between natural and urban environments. We found that the home ranges were smaller in urban environments compared with natural environments (mean effect size = -0.844), and we observed a similar result when considering birds and mammals separately. We also found that home range sizes were not significantly affected when disturbance in urban areas was minimal, which suggests that many species may be able to tolerate low levels of disturbance without changing their movement patterns. Our study thus indicates that increasing levels of urbanisation restrict the spatial movement of species across taxa; this information is relevant for ecological studies of further urban species as well as for the development of management strategies for urban populations

Tardigrades in the city: A review of diversity patterns in response to urbanization

In different taxonomical groups, the number of species found in urban environments tends to decline compared to adjacent nonurban environments. It is unclear whether tardigrades also conform to this pattern of diversity decline in cities. Tardigrades are microscopic invertebrates which have been understudied, despite the fact that they are cosmopolitan and found in all types of habitats. Due to their capability to withstand extreme conditions, tardigrades should be able to successfully thrive in urban environments. Here, all available information about tardigrade diversity in cities was compiled. It was quantitatively determined that tardigrade diversity declines in urban areas compared to adjacent rural areas. Geographically, closer cities are also likely to harbor a more similar set of tardigrade species. In comparison to other groups like mammals and birds, there are no tardigrade species consistently found in most studied cities. In fact, most urban tardigrades have only been found in one single city. Ultimately, the species of tardigrades found in a given city will normally depend on the set of species already living in the adjacent native environments. One question that deserves further investigation is why only a subset of such native species is able to colonize the new environmental niches available in cities

Importance of Taxonomic Group, Life Stage and Circumstance of Rescue upon Wildlife Rehabilitation in Ontario, Canada

Wildlife rehabilitation is an increasingly important and global practice, aiming towards advancements in animal welfare and species conservation. Although there are ongoing discussions on the benefits and limitations of wildlife rehabilitation, there is a general agreement on the importance of wildlife rehabilitation on improving the welfare of wild animals and identifying threats to wildlife. Determining which factors lead to a successful outcome of rehabilitation can allow wildlife rehabilitation centres to best focus their resources to benefit animals with the greatest chance of a successful release. In this study, three factors affecting the success of rehabilitation were evaluated: taxonomic group, life stage and circumstance of rescue. We used a large database of patients’ records (9561 animals from 198 species) from Sandy Pines Wildlife Centre (Ontario, Canada) over a three year study period (from 2015 to 2018). We found that reptiles had a higher rate of release (63.6 %), compared with mammals (42.1 %) and birds (48.3 %), although released reptiles spent longer in the centre than birds and mammals. Animals arriving to the centre in poor condition were less likely to be rehabilitated and spent longer in the centre than animals arriving in good condition. Overall, preadults were more likely to be released than adults, although the number of days spent at the centre did not differ by life stage. Animals suffering active damage (e.g. ‘collision’ and ‘projectile’) were less likely to be rehabilitated than animals suffering passive damage (e.g. arriving to the centre as ‘orphan’ or due to ‘habitat destruction’); however, when only considering those animals that left the centre, the number of days spent at the centre did not differ between animals suffering passive or active damage. The analysis of patients’ records can provide relevant information to rehabilitators about factors influencing rehabilitation efforts, which can be used to implement strategies that maximise release rates, given limited resources

Two modes of input processing in relation to risk of sperm competition in mammals

Much research has been focused on the ‘output’ or response of males to particular risks of sperm competition (RSC). Lately, there has also been some interest on the types of information that males may use to assess RSC (RSC inputs). In contrast, there is a lack of studies on how males may process RSC inputs to generate such RSC outputs. Here we propose two modes of input processing (direct and indirect) and ways to test them in order to understand how a male may process and store RSC information. The direct mode of input processing predicts that a male may store RSC inputs through a physiological response, e.g., through a change in hormonal levels. As long as this response is active, the male will stay in a ‘RSC state’ and will produce an RSC output (e.g. high sperm investment) instead of a non-RSC output (e.g. relatively lower sperm investment) when he encounters a female. The indirect mode of input processing predicts that a male may store RSC inputs in his memory and retrieve such information later on to modify his output (e.g. sperm investment or copulatory behavior) accordingly. We use a multidisciplinary approach that should appeal to those researchers that seek to understand male’s adaptations to sperm competition at different levels. We believe that the testing of the hypotheses developed in this paper will lead to interesting findings and the development of new hypothese

Shyer and larger bird species show more reduced fear of humans when living in urban environments

As the natural habitats of many species are degraded or disappear, there is scope for these species to be established in urban habitats. To ease the establishment and maintenance of urban populations of more species we need to better understand what degree of phenotypical change to expect as different species transition into urban environments. During the first stages of urban colonization, behavioural changes such as an increase in boldness are particularly important. A consistent response in urban populations is to decrease the distance at which individuals flee from an approaching human (flight initiation distance, or FID). Performing a phylogenetic generalized least-squares (PGLS) analysis on 130 avian species, I found that the largest changes in FID between rural and urban populations occur in species that are larger-bodied and naturally shy (higher rural FID), two phenotypic traits that are not normally associated with urban colonizers. More unlikely species may thus be able to colonize urban environments, especially if we design cities in ways that promote such urban colonizations

Not all cities are the same: variation in animal phenotypes across cities within urban ecology studies

The sustained expansion of urban environments has been paralleled by an increase in the number of studies investigating the phenotypic changes of animals driven by urbanization. Most of these studies have been confined to only one urban center. However, as the types and strength of anthropogenic stressors differ across cities, a generalizable understanding of the effects of urbanization on urban-dwelling species can only be reached by comparing the responses of urban populations from the same species across more than one city. We conducted phylogenetic meta-analyses on data for animal species (including both invertebrates and vertebrates) for which measures about any morphological, physiological, or behavioral trait were reported for two or more cities. We found that morphological, physiological and behavioral traits of urban animals all differ similarly across cities, and that such phenotypic differences across cities increase as the more cities were investigated in any given study. We also found support for phenotypic differences across cities being more pronounced as the farther away cities are from each other. Our results clearly indicate that separate urban populations of the same species can diverge phenotypically, and support previous pleas from many researchers to conduct urban studies across several urban populations. We particularly recommend that future studies choose cities in different biomes, as urban adaptations may differ substantially in cities sited in different ecological matrices. Ultimately, a generalized knowledge about how organisms are affected by urbanization will only be possible when comprehensive biological patterns are similarly studied across separate and distinct cities

Effects of metabolic rate and sperm competition on the fatty-acid composition of mammalian sperm

The sperm membrane is a key structure affecting sperm function and thus reproductive success. Spermatozoa are highly specialized and differentiated cells that undergo a long series of processes in the male and female reproductive tracts until they reach the site of fertilization. During this transit, the sperm membrane is prone to damage such as lipid peroxidation. The characteristics and performance of the sperm membrane are strongly determined by the fatty-acid composition of membrane phospholipids. Polyunsaturated fatty-acids (PUFAs) are the most prone to lipid peroxidation. Lipid peroxidation and other types of oxidative damage increase with higher metabolism and with higher levels of sperm competition due to the increased ATP production to fuel higher sperm velocities. Consequently, we hypothesized that, in order to avoid oxidative damage, and the ensuing impairment of sperm function, sperm cells exhibit a negative relationship between PUFA content and mass-specific metabolic rate (MSMR). We also hypothesized that higher sperm competition leads to a reduction in the proportion of sperm PUFAs. We performed a comparative study in mammals and found that high MSMR and high levels of sperm competition both promote a decrease in the proportion of PUFAs that are more prone to lipid peroxidation. The negative relationship between MSMR and these PUFAs in sperm cells is surprising, because a positive relationship is found in all other cell types so far investigated. Our results support the idea that the effects of MSMR and sperm competition on sperm function can operate at very different levels. © 2013 European Society For Evolutionary Biology.This work was supported by a Ramón y Cajal fellowship (RYC-2011-07943) to J.d.-T. and grants from the Spanish Ministry of Economy and Competitiveness (CGL2011-26341 to E.R.S.R. and CGL2012-37423 to J.d.-T.).Peer Reviewe

Differences in the fatty-acid composition of rodent spermatozoa are associated to levels of sperm competition.

Sperm competition is a prevalent phenomenon that drives the evolution of sperm function. High levels of sperm competition lead to increased metabolism to fuel higher sperm velocities. This enhanced metabolism can result in oxidative damage (including lipid peroxidation) and damage to the membrane. We hypothesized that in those species experiencing high levels of sperm competition there are changes in the fatty-acid composition of the sperm membrane that makes the membrane more resistant to oxidative damage. Given that polyunsaturated fatty acids (PUFAs) are the most prone to lipid peroxidation, we predicted that higher sperm competition leads to a reduction in the proportion of sperm PUFAs. In contrast, we predicted that levels of sperm competition should not affect the proportion of PUFAs in somatic cells. To test these predictions, we quantified the fatty-acid composition of sperm, testis and liver cells in four mouse species (genus Mus) that differ in their levels of sperm competition. Fatty-acid composition in testis and liver cells was not associated to sperm competition levels. However, in sperm cells, as predicted, an increase in sperm competition levels was associated with an increase in the proportion of saturated fatty-acids (the most resistant to lipid peroxidation) and by a concomitant decrease in the proportion of PUFAs. Two particular fatty acids were most responsible for this pattern (arachidonic acid and palmitic acid). Our findings thus indicate that sperm competition has a pervasive influence in the composition of sperm cells that ultimately may have important effects in sperm function