Mating system drives negative associations between morphological features in Schistosomatidae

Abstract

Background: Sexual morphological features are known to be associated with the mating systems of several animal groups. However, it has been suggested that morphological features other than sexual characteristics could also be constrained by the mating system as a consequence of negative associations. Schistosomatidae are parasitic organisms that vary in mating system and can thus be used to explore links between the mating system and negative associations with morphological features.

Results: A comparative analysis of Schistosomatidae morphological features revealed an association between the mating system (monogamous versus polygynandrous) and morphological characteristics of reproduction, nutrition, and locomotion.

Conclusions: The mating system drives negative associations between somatic and sexual morphological features. In monogamous species, males display a lower investment in sexual tissues and a higher commitment of resources to tissues involved in female transport, protection, and feeding assistance. In contrast, males of polygynandrous species invest to a greater extent in sexual tissues at the cost of reduced commitment to female care.

Figure 1

Morphological features recorded. A. Schistosome pair. B. Male schistosome C. Female schistosome

Figure 2

Phylogenetic supertree of several species from the family Schistosomatidae, obtained from phylogenetic analyses based on partial 18S and 28S rDNA, and CO1 mtDNA. Numbers near branches are posterior probabilities indicating clade support. These numbers and branch lengths were computed using Bayesian inference based on 28S rDNA sequences (see text for details). Species in regular, bold and italic characters are polygynandrous, polygynous and monogamous, respectively.

Figure 3

The influence of monogamous (grey histogram) versus polygynandrous (white histogram) mating systems on Schistosomatidae morphological features with implications for reproduction (A), nutrition (B) or locomotion (C). *Statistically significant difference using Mann-Whitney U-tests. Pie charts display the variation partitioning between phylogeny in white, mating system in grey, and the overlap between these two components in black. The P-value of the shares evaluation appears above the pie chart. The number above each histogram corresponds to the sample size.