Testing for phylogenetic signal in claws suggests great influence of ecology on Caribbean intertidal arthropods (Acari, Oribatida)

Michaela Kerschbaumer,Tobias Pfingstl

doi:10.1038/s41598-021-83747-3

Abstract

Claws are common biological attachment devices that can be found in a wide variety of animal groups. Their curvature and size are supposed to be parameters related to ecological aspects. Mites, known as very small arthropods, occupy a wide range of ecological niches and are a perfect model system to investigate correlations of claw morphology with ecology. There is only one study regarding this question in littoral mites but the phylogenetic impact, which plays an important role in the evolution of morphological traits, was not tested. We investigated claw shapes of different Caribbean populations of five species showing different substrate/habitat preferences. We used geometric morphometrics to quantify claw shape and tested for phylogenetic signal within this morphological trait. Even in closely related populations, we found clear claw shapes for hard versus soft substrate, confirming previous findings. Surprisingly, we found no phylogenetic signal within the trait, which demonstrates that ecology (different surfaces and substrates) has acted as one of the primary selective forces in the diversification of claw shapes. Considering that the basic claw design may be the same in the majority of arthropods, our results have important implications for further investigations of claw morphology and its ecological relevance within this phylum.

Highlights

Claws are common biological attachment devices that can be found in a wide variety of animal groups
We investigated the claw shapes of five different intertidal oribatid mite species from the Caribbean belonging to two different families and showing different substrate/habitat preferences
Using this specific setup of focal species, i.e. distinct species versus closely related species/lineages with differing distributions and identical or diverging ecologies, we aimed to answer the following questions: (I) can the ecomorphological types of shape inferred by Pfingstl et al.[12] be confirmed on different phylogenetic levels, (II) what is the exact interplay between claw morphology, microhabitat use and phylogenetic relatedness and (III) how strong is the phylogenetic signal in these claw shapes

Summary

Introduction

Claws are common biological attachment devices that can be found in a wide variety of animal groups. The fortuyniid Litoribates bonairensis and Litoribates floridae are distinct species which show very limited distributions and are classified as typical mangrove dwellers[19]; the selenoribatid Thalassozetes barbara shows a trans-Caribbean distribution and exclusively inhabits rocky habitats; and Carinozetes bermudensis and Carinozetes mangrovi, show a wide Caribbean distribution but consist of five distinct genetic lineages, three of these lineages occur on a variety of substrates, whereas the remaining two lineages exclusively dwell either on rocky substrate or in mangrove habitats[19] Using this specific setup of focal species, i.e. distinct species versus closely related species/lineages with differing distributions and identical or diverging ecologies, we aimed to answer the following questions: (I) can the ecomorphological types of shape inferred by Pfingstl et al.[12] be confirmed on different phylogenetic levels, (II) what is the exact interplay between claw morphology, microhabitat use and phylogenetic relatedness and (III) how strong is the phylogenetic signal in these claw shapes

Objectives

Methods

Results

Conclusion