Male red throat coloration, pelvic spine coloration, and courtship behaviours in threespine stickleback

Background: In addition to exhibiting red nuptial throat coloration, male threespine sticklebacks (Gasterosteus aculeatus) often possess red coloration on their pelvic spines. Although variation in throat colour has been shown to be associated with male reproductive behaviour, limited research has been devoted to the behavioural correlates of red spine colour. Like the red throat, spine colour might correlate with components of male reproductive behaviour and may also be androgen dependent, with important implications for a potential signalling function. Hypothesis: Spine coloration, like throat coloration, is correlated with components of courtship behaviour, and also with the fish androgen 11-ketotestosterone (11KT). Methods: To examine the role of male throat and spine colour expression in a mating context, we measured the behavioural response of nesting males to conspecific females. We analysed the relationships between throat and spine colours with reproductive behaviours as well as with 11KT. Results: Males with more intensely red throats courted females more vigorously, whereas males with redder spines displayed relatively more aggressive behaviour during courtship. An initial analysis of a subsample of males showed that 11KT was positively associated with spine colour intensity, but not with red throats or any behaviours. Hence throat and spine colour may reflect different components of male reproductive behaviour, and 11KT is a potential mediator of spine coloration in males

Conspicuous Female Ornamentation and Tests of Male Mate Preference in Threespine Sticklebacks (Gasterosteus aculeatus)

Sexual selection drives the evolution of exaggerated male ornaments in many animal species. Female ornamentation is now acknowledged also to be common but is generally less well understood. One example is the recently documented red female throat coloration in some threespine stickleback (Gasterosteus aculeatus) populations. Although female sticklebacks often exhibit a preference for red male throat coloration, the possibility of sexual selection on female coloration has been little studied. Using sequential and simultaneous mate choice trials, we examined male mate preferences for female throat color, as well as pelvic spine color and standard length, using wild-captured threespine sticklebacks from the Little Campbell River, British Columbia. In a multivariate analysis, we found no evidence for a population-level mate preference in males, suggesting the absence of directional sexual selection on these traits arising from male mate choice. Significant variation was detected among males in their preference functions, but this appeared to arise from differences in their mean responsiveness across mating trials and not from variation in the strength (i.e., slope) of their preference, suggesting the absence of individual-level preferences as well. When presented with conspecific intruder males, male response decreased as intruder red throat coloration increased, suggesting that males can discriminate color and other aspects of phenotype in our experiment and that males may use these traits in intrasexual interactions. The results presented here are the first to explicitly address male preference for female throat color in threespine sticklebacks.Open Access Publishing Fun

Origin, maintenance and evolutionary consequences of male mating preference variation in East African cichlid fishes

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Differences in male coloration are predicted by divergent sexual selection between populations of a cichlid fish

Female mating preferences can influence both intraspecific sexual selection and interspecific reproductive isolation, and have therefore been proposed to play a central role in speciation. Here, we investigate experimentally in the African cichlid fish Pundamilia nyererei if differences in male coloration between three para-allopatric populations (i.e. island populations with gene flow) of P. nyererei are predicted by differences in sexual selection by female mate choice between populations. Second, we investigate if female mating preferences are based on the same components of male coloration and go in the same direction when females choose among males of their own population, their own and other conspecific populations and a closely related para-allopatric sister-species, P. igneopinnis. Mate-choice experiments revealed that females of the three populations mated species-assortatively, that populations varied in their extent of population-assortative mating and that females chose among males of their own population based on different male colours. Females of different populations exerted directional intrapopulation sexual selection on different male colours, and these differences corresponded in two of the populations to the observed differences in male coloration between the populations. Our results suggest that differences in male coloration between populations of P. nyererei can be explained by divergent sexual selection and that population-assortative mating may directly result from intrapopulation sexual selection

Data from: The peril of proportions: robust niche indices for categorical data

Indices of niche breadth and niche overlap for categorical data are typically expressed in terms of proportions of resources use. These are unit-sum constrained data; hence, direct application of standard general linear modelling methods to such indices can lead to spurious correlations and misleading inference. To overcome these limitations, we introduce a compositional data analysis (CoDA) approach and derive compositional expressions of niche breadth, niche overlap and specialization. Compositional data analysis is specifically devoted to the analysis of vectors of proportions (i.e. compositions) and represents the appropriate framework for the study of sets of data with unit-sum constraint as those typically used in the calculation of niche indices. We show that compositional indices exhibit suitable statistical properties that make them flexible and robust, allowing downstream application of the full toolbox of multivariate analysis techniques to these estimators, a possibility not available with classical indices. In addition, we find that when characterizing niche breadth, niche overlap and specialization in terms of vectors of proportions, these concepts are naturally integrated in a coherent unifying framework. When data are categorical, we recommend the use of compositional indices for the statistical analysis of specialization metrics, niche breadth and niche overlap. We believe that the unified framework emerging from our compositional approach to niche metrics will allow a more thorough understanding of specialization at multiple levels of biological organization and provide novel insights in complex phenomena such as invasions and niche shifts

Lens transmittance shapes ultraviolet sensitivity in the eyes of frogs from diverse ecological and phylogenetic backgrounds

The amount of short wavelength (ultraviolet (UV), violet and blue) light that reaches the retina depends on the transmittance properties of the ocular media, especially the lens, and varies greatly across species in all vertebrate groups studied previously. We measured the lens transmittance in 32 anuran amphibians with different habits, geographical distributions and phylogenetic positions and used them together with eye size and pupil shape to evaluate the relationship with diel activity pattern, elevation and latitude. We found an unusually high lens UV transmittance in the most basal species, and a cut-off range that extends into the visible spectrum for the rest of the sample, with lenses even absorbing violet light in some diurnal species. However, other diurnal frogs had lenses that transmit UV light like the nocturnal species. This unclear pattern in the segregation of ocular media transmittance and diel activity is shared with other vertebrates and is consistent with the absence of significant correlations in our statistical analyses. Although we did not detect a significant phylogenetic effect, closely related species tend to have similar transmittances, irrespective of whether they share the same diel pattern or not, suggesting that anuran ocular media transmittance properties might be related to phylogeny

Examining Indices of Individual-level Resource Specialization

The variety of resources that a population exploits is known as the “niche width”. A particular population has a narrow niche if only few kinds of the available resources are exploited by its members. When the individuals of a population exploit many different resources, then the population has a wide niche. From this point of view it seems that the niche is a property of the population as a whole. However, it is well known that many apparently generalist populations are in fact composed of individual specialists, that is, members that use only small subsets of the population’s niche. This approach justifies the definition of indices to measure the individual-level resource specialization. Although this kind of analysis could be applied to any niche variation: oviposition sites, habitat, etc., we focus the discussion in terms of analysis of diet data. So as to measure species niche breadth a comparison between the frequency distribution of the species’ resource use with that of all available resources is carried out. When a measure of individual specialization is considered, then one should compare the population’s total diet with the individual use. In particular, the total niche width of a population should be compared with its two components: within and between-individual variation. In this sense, in the literature several indices of intrapopulation niche variation are proposed. Our goal is to describe, compare and evaluate four of the most relevant indices applied in ecology. In this work we point out how these techniques could be developed in a compositional framework, particularly when these indices are applied to discrete diet data [e.g. frequency of different prey specimen in the diet]

Gracilinanus_microtarsus_diet

Diet data of the gracile mouse opossum Gracilinanus microtarsus from Araujo et al. (2010), Oikos 119: 81-88, kindly provided by Dr Mauricio Araujo to Pierotti, Martin-Fernandez & Barcelo-Vidal for the simulations performed in this paper