Disentangling the Size and Shape Components of Sexual Dimorphism

Cheng, Ren-Chung; Kuntner, Matjaž

doi:10.1007/s11692-015-9313-z

Cited by 25 publications

(20 citation statements)

References 79 publications

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“…Species of the genus Argiope are large, sexually dimorphic, charismatic spiders with brightly colored abdomens (Cheng and Kuntner 2014, 2015) that were noted by early taxonomists and among the first spiders to be described (Catalog 2015; Clerck 1757). Despite their large adult size, Argiope spiders are thought to be excellent dispersers because they occupy open tree-less habitats and have been documented to balloon (Bell et al 2005).…”

Section: Introductionmentioning

confidence: 99%

Phylogeography of a good Caribbean disperser: Argiope argentata (Araneae, Araneidae) and a new ‘cryptic’ species from Cuba

Agnarsson¹,

LeQuier²,

Kuntner³

et al. 2016

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The Caribbean islands harbor rich biodiversity with high levels of single island endemism. Stretches of ocean between islands represent significant barriers to gene-flow. Yet some native species are widespread, indicating dispersal across oceans, even in wingless organisms like spiders. Argiope argentata (Fabricius, 1775) is a large, charismatic, and widespread species of orb-weaving spider ranging from the United States to Argentina and is well known to balloon. Here we explore the phylogeography of Argiope argentata in the Caribbean as a part of the multi-lineage CarBio project, through mtDNA haplotype and multi-locus phylogenetic analyses. The history of the Argiope argentata lineage in the Caribbean goes back 3-5 million years and is characterized by multiple dispersal events and isolation-by-distance. We find a highly genetically distinct lineage on Cuba which we describe as Argiope butchko sp. n. While the argentata lineage seems to readily balloon shorter distances, stretches of ocean still act as filters for among-island gene-flow as evidenced by distinct haplotypes on the more isolated islands, high FST values, and strong correlation between intraspecific (but not interspecific) genetic and geographic distances. The new species described here is clearly genetically diagnosable, but morphologically cryptic, at least with reference to the genitalia that typically diagnose spider species. Our results are consistent with the intermediate dispersal model suggesting that good dispersers, such as our study species, limit the effect of oceanic barriers and thus diversification and endemism.

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Section: Introductionmentioning

confidence: 99%

Phylogeography of a good Caribbean disperser: Argiope argentata (Araneae, Araneidae) and a new ‘cryptic’ species from Cuba

Agnarsson¹,

LeQuier²,

Kuntner³

et al. 2016

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“…However, SSD, an evolutionary phenomenon where the sexes exhibit considerable size differences [ 11 – 16 ], is much better understood than SGD. Furthermore, while research on clades with male-biased SSD may have converged on its causes and consequences that relate to sexual selection [ 17 – 20 ], in clades that exhibit a strong female-biased SSD, such as many invertebrates, size evolution responds to a mix of sexual and natural selection [ 13 , 21 – 25 ].…”

Section: Introductionmentioning

confidence: 99%

Coevolution of female and male genital components to avoid genital size mismatches in sexually dimorphic spiders

2016

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BackgroundIn most animal groups, it is unclear how body size variation relates to genital size differences between the sexes. While most morphological features tend to scale with total somatic size, this does not necessarily hold for genitalia because divergent evolution in somatic size between the sexes would cause genital size mismatches. Theory predicts that the interplay of female-biased sexual size dimorphism (SSD) and sexual genital size dimorphism (SGD) should adhere to the ‘positive genital divergence’, the ‘constant genital divergence’, or the ‘negative genital divergence’ model, but these models remain largely untested. We test their validity in the spider family Nephilidae known for the highest degrees of SSD among terrestrial animals.ResultsThrough comparative analyses of sex-specific somatic and genital sizes, we first demonstrate that 99 of the 351 pairs of traits are phylogenetically correlated. Through factor analyses we then group these traits for MCMCglmm analyses that test broader correlation patterns, and these reveal significant correlations in 10 out of the 36 pairwise comparisons. Both types of analyses agree that female somatic and internal genital sizes evolve independently. While sizes of non-intromittent male genital parts coevolve with male body size, the size of the intromittent male genital parts is independent of the male somatic size. Instead, male intromittent genital size coevolves with female (external and, in part, internal) genital size. All analyses also agree that SGD and SSD evolve independently.ConclusionsInternal dimensions of female genitalia evolve independently of female body size in nephilid spiders, and similarly, male intromittent genital size evolves independently of the male body size. The size of the male intromittent organ (the embolus) and the sizes of female internal and external genital components thus seem to respond to selection against genital size mismatches. In accord with these interpretations, we reject the validity of the existing theoretical models of genital and somatic size dimorphism in spiders.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-016-0734-9) contains supplementary material, which is available to authorized users.

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“…Males and females of the same species can differ in size (Fairbairn et al 2007), shape (Herrel et al 2010, Cheng andKuntner 2015), and the presence/absence of extravagant structures (e.g. horns in beetles; Emlen et al 2005).…”

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Broad‐scale variation in sexual dichromatism in songbirds is not explained by sex differences in exposure to predators during incubation

Matysioková

Remeš

Cockburn

2017

Journal of Avian Biology

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The evolution of sexual dichromatism provoked one of the greatest disagreements between Charles Darwin and Alfred Russel Wallace. According to Darwin the main driving force is sexual selection, whereby choosy females prefer showy males, leading to the evolution of conspicuous male plumage. On the other hand, Wallace suggested that dichromatism may arise because nest predation favors more cryptic females. To test the role of natural selection in the evolution of dichromatism we combined quantitative data on differences in parental share in nest attentiveness (representing the strength of natural selection on males vs females) with spectrophotometric measurements of dichromatism in 412 species of songbirds from 69 families. We expected to find stronger dichromatism in open‐nesting species with more divergent parental roles and in body parts exposed during incubation. Dichromatism was not related to the differences in parental share during incubation, but it was most pronounced in lekking species, migrants, and small species. Our results thus suggest that Wallace's hypothesis is not able to explain broad‐scale variation in the dichromatism of songbirds, but point to a role for sexual selection, mutual mate choice, and migration strategy in shaping the extraordinary variation in dichromatism exhibited by songbirds.

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Disentangling the Size and Shape Components of Sexual Dimorphism

Cited by 25 publications

References 79 publications

Phylogeography of a good Caribbean disperser: Argiope argentata (Araneae, Araneidae) and a new ‘cryptic’ species from Cuba

Phylogeography of a good Caribbean disperser: Argiope argentata (Araneae, Araneidae) and a new ‘cryptic’ species from Cuba

Coevolution of female and male genital components to avoid genital size mismatches in sexually dimorphic spiders

Broad‐scale variation in sexual dichromatism in songbirds is not explained by sex differences in exposure to predators during incubation

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