About This Project

Most animal species have populations with equal ratios of males and females, but some have naturally biased sex ratios. There are are many factors that cause the bias to occur-- so what happens to the under-represented sex of a species over evolutionary time? I will investigate by studying the morphology and genetics of a female-biased daddy-longlegs species (Leiobunum relictum) that seems to only occur in the geologically-unique Wichita Mountains of Oklahoma.

Ask the Scientists

What is the context of this research?

Recently, I made discoveries about two species of harvestmen in Japan that have females that can reproduce both sexually and asexually. The first cool discovery was that males of these species have adaptations that may make them better at coercing females to mate. The second: these adaptations are more pronounced in individuals that come from populations where males are rarer than females.

This got me thinking about a case closer to home: the species Leiobunum relictum. Based on museum collections, this species may have female bias too. It seems females of this species lack the pre-genital protection their close relatives have. I wondered: do females of L. relictum reproduce asexually? And, are males dying out, or adapting to coercion?

What is the significance of this project?

There has recently been a lot of interest both within and outside the scientific community regarding how external factors adjust the morphology of a species over evolutionary time. I think it is possible that sex ratio bias, whether caused by endosymbionts (bacteria living within hosts) or by other forms of parthenogenesis (asexual reproduction that doesn't require fertilization), may over time put selective pressure on males to be extra good at coercing females to mate. Otherwise, females might just reproduce asexually all the time!

Moreover, we are starting to see lots of studies that focus on daddy-longlegs. I think this is great, because North America is full of them! It is high time that we learned more about the biodiversity of the species that we see everyday.

What are the goals of the project?

My first goal is to travel to the Wichita Mountains, Oklahoma, and National Forest sites in Arkansas to collect Leiobunum relictum and its closely related species. I will go in early June 2017, when adults are present, and collect and preserve as many L. relictum, L. vittatum, and L. crassipalpe as I am able to find. Specimens will be collected by hand and sweep net, and I will document locations via GPS.

My second goal will be to extract, sequence, and analyze the DNA of specimens to learn 1) whether L. relictum is genetically a separate species, 2) when samples from the Wichita Mtns. diverged, and 3) if samples are infected with bacteria that causes male death. I will also examine the reproductive organs of all samples I collect.