scholarly journals Phylogenetic Evidence for the Gain and Loss of a Sexually Selected Trait in Sailfin Mollies

ISRN Zoology ◽  
2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
Margaret B. Ptacek ◽  
Michael J. Childress ◽  
Jennifer A. Petersen ◽  
Anne O. Tomasso
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Large Male ◽  
Comparative Approach ◽  
Character State ◽  
Male Size ◽  
Ancestral Character State ◽  
Sailfin Molly ◽  
Monophyletic Lineage ◽  
Sailfin Mollies

A phylogenetic comparative approach was used to examine the evolution of the enlarged “sailfin,” characteristic of the monophyletic lineage of sailfin mollies (Poecilia: Mollienesia), but absent in one of its species, P. latipunctata. Ancestral character state reconstructions demonstrated that the ancestral sailfin molly possessed the enlarged sailfin, and, thus, males of P. latipunctata have secondarily lost this trait. The strength of female mating preference was measured in P. latipunctata for two known targets of sexual selection, large male size, and sailfin male phenotype. Females of P. latipunctata preferred conspecific males of larger body size to those of smaller body size, but showed no preference for sailfin males of a related species, P. velifera, when compared with males of the shortfin species, P. mexicana. Taken together, these results suggest that the targets of sexual selection may have shifted in this species and that reduction in female preference for sailfin males may have played a role in the loss of this ornament.

scholarly journals Does divergence in female mate choice affect male size distributions in two cave fish populations?

2008 ◽  
Vol 4 (5) ◽  
pp. 452-454 ◽  
Author(s):  
Michael Tobler ◽  
Ingo Schlupp ◽  
Martin Plath
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Mate Choice ◽  
Female Choice ◽  
Female Mate Choice ◽  
Female Preference ◽  
Large Male ◽  
Male Body ◽  
Male Size ◽  
Female Mate

Sexual selection by female choice can maintain male traits that are counter selected by natural selection. Alteration of the potential for sexual selection can thus lead to shifts in the expression of male traits. We investigated female mate choice for large male body size in a fish ( Poecilia mexicana ) that, besides surface streams, also inhabits two caves. All four populations investigated, exhibited an ancestral visual preference for large males. However, only one of the cave populations also expressed this female preference in darkness. Hence, the lack of expression of female preference in darkness in the other cave population leads to relaxation of sexual selection for large male body size. While P. mexicana populations with size-specific female mate choice are characterized by a pronounced male size variation, the absence of female choice in one cave coincides with the absence of large bodied males in that population. Our results suggest that population differences in the potential for sexual selection may affect male trait variation.

Size does not matter for male Marbled Salamanders (Ambystoma opacum)

2015 ◽  
Vol 93 (10) ◽  
pp. 735-740
Author(s):  
D.A. Croshaw ◽  
J.H.K. Pechmann
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Reproductive Success ◽  
Large Male ◽  
Male Mating ◽  
Ambystoma Opacum ◽  
Positive Assortative Mating ◽  
Important Trait ◽  
Breeding Groups ◽  
Gravid Females

Understanding the phenotypic attributes that contribute to variance in mating and reproductive success is crucial in the study of evolution by sexual selection. In many animals, body size is an important trait because larger individuals enjoy greater fitness due to the ability to secure more mates and produce more offspring. Among males, this outcome is largely mediated by greater success in competition with rival males and (or) advantages in attractiveness to females. Here we tested the hypothesis that large male Marbled Salamanders (Ambystoma opacum (Gravenhorst, 1807)) mate with more females and produce more offspring than small males. In experimental breeding groups, we included males chosen specifically to represent a range of sizes. After gravid females mated and nested freely, we collected egg clutches and genotyped all adults and samples of hatchlings with highly variable microsatellite markers to assign paternity. Size had little effect on male mating and reproductive success. Breeding males were not bigger than nonbreeding males, mates of polyandrous females were not smaller than those of monogamous females, and there was no evidence for positive assortative mating by size. Although body size did not matter for male Marbled Salamanders, we documented considerable fitness variation and discuss alternative traits that could be undergoing sexual selection.

scholarly journals Male size and reproductive performance in three species of livebearing fishes (Gambusia spp.): a systematic review and meta-analysis

2021 ◽  
Author(s):  
Bora Kim ◽  
Nicholas Patrick Moran ◽  
Klaus Reinhold ◽  
Alfredo Sánchez-Tójar
Keyword(s):  
Systematic Review ◽  
Sexual Selection ◽  
Body Size ◽  
Confidence Interval ◽  
Reproductive Performance ◽  
Female Choice ◽  
Meta Analysis ◽  
Male Body ◽  
Male Size ◽  
Male Body Size

1. The genus Gambusia represents approximately 45 species of polyandrous livebearing fishes with reversed sexual size dimorphism (i.e. males smaller than females) and with copulation predominantly via male coercion. Male body size has been suggested as an important sexually selected trait, but despite abundant research, evidence for sexual selection on male body size in this genus is mixed. 2. Studies have found that large males have an advantage in both male-male competition and female choice, but that small males perform sneaky copulations better and at higher frequency and thus may sire more offspring in this coercive mating system. Here, we synthesized this discrepant body of evidence in the primary literature. 3. Using pre-registered methods and hypotheses, we performed a systematic review and meta-analysis combining published (n = 19 studies, k = 106 effect sizes) and unpublished data (n = 17, k = 242) to test whether there is overall selection on male body size across studies in Gambusia. We also tested several specific hypotheses to understand sources of heterogeneity across effects. 4. Meta-analysis revealed an overall positive correlation between male size and reproductive performance (r = 0.23, 95% confidence interval: 0.10 – 0.35, n = 36, k = 348, 4514 males, three Gambusia species). Despite high heterogeneity, the large-male advantage appeared robust across all measures studied (i.e. female choice, mating success, paternity, sperm quantity and quality), but was considerably larger for female choice (r = 0.43, 95% confidence interval: 0.28 – 0.59, n = 14, k = 43). Meta-regressions found several important factors explaining heterogeneity across effects, including type of sperm characteristic, male-to-female ratio, female reproductive status, and environmental conditions. We found evidence of publication bias; however, its effect on our estimates was attenuated by including a substantial amount of unpublished effects, highlighting the importance of unpublished (open) data for more accurate meta-analytic estimates. 5. In addition to positive selection on male size, our study suggests that we need to rethink the role and form of sexual selection in Gambusia and, more broadly, to consider the ecological factors that affect reproductive behaviour in livebearing fishes.

The role of phylogeny in quantitative paleobiological data analysis

Paleobiology ◽  
2001 ◽  
Vol 27 (2) ◽  
pp. 226-240 ◽  
Author(s):  
Norman MacLeod
Keyword(s):  
Data Analysis ◽  
Planktonic Foraminifera ◽  
Active Role ◽  
Comparative Approach ◽  
Character State ◽  
Data Set ◽  
Ancestral Character State ◽  
Branch Lengths ◽  
Recent Species ◽  
Phylogenetic Perspective

Phylogenies provide a rich source of information that should be exploited in designing quantitative hypothesis tests in paleobiological contexts. Viewing such data analysis problems through the prism of phylogenetically structured comparisons can help add realism and depth to paleobiological data-analysis strategies. Two examples of the importance of adopting a phylogenetic perspective are discussed. In the first example, a phylogenetic-comparative approach is used to test correlations between ecological, morphological, and biological characteristics of planktonic foraminifera. Results suggest that the presence of spines and photosynthetic symbionts in Neogene-Recent species are not adaptations to living in shallow-intermediate planktonic depth habitats. In the second, a phylogenetic-comparative approach is used to reveal the presence of morphological correlations with locomotor function in a mammalian carnivore data set. Paleontologists can play an active role in improving comparative data analyses by (1) helping to develop improved phylogenies, especially those that provide better estimates of branch lengths, and (2) helping to resolve a number of outstanding issues surround the question of ancestral character-state specification.

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