Fly mating choices may help explain variation across species

September 19, 2018

Scientists at the University of Stirling have shed new light on the impact of sexual selection on species diversity after studying the mating rituals of dance flies.

The team, from the Faculty of Natural Sciences, examined the unique mating behaviour of Rhamphomyia longicauda - the long-tailed dance fly - in a bid to understand how species evolve.

Some female dance flies exhibit extravagant sexual ornaments - characteristics to help attract mating partners - which is unusual because, in other animals, such traits are typically observed in males. Examples include peacocks, which use their tail feathers to advertise their sexual and physical fitness and male black grouse, which attract partners by singing, dancing and showing their tail fans.

In dance flies, some females use their hairy legs and inflatable abdominal sacs to make themselves appear bigger - and more attractive - to potential partners.

Dr Luc Bussière, a Lecturer in Biological and Environmental Sciences, worked on the research alongside PhD student Rosalind Murray and colleagues at the University of Toronto.

"Generally speaking, females do not have any sexual ornaments at all - they are typically a male characteristic," explained Dr Bussière. "Our study looked at this species and considered why females had ornaments and what exactly attracted the males to their partners.

"Interestingly, the research found that females often deceive males by attempting to make themselves appear bigger - and ultimately more attractive - than they actually are. In contrast, the males are constantly evolving in an attempt to avoid being duped.

"This work supports our understanding of how sexual selection creates diversity and, in turn, can help us to provide an answer to one of the biggest questions in biology: why are there so many different species?"

Large female dance flies may be more attractive to males because they appear to be full of eggs - enhancing males' opportunity to father offspring - and during each mating process, the male "gifts" food to the female.

The scientists wanted to understand the significance of each of the female's sexual ornaments and, in a bid to gain a greater insight into the preferences of males, they used artificial physical models of females in the wild, combining varying sizes of abdominal and leg ornaments. The team were then able to count how much interest each artificial model attracted from wild males.

"We found that males like both large bodies and hairy legs, but were much more attracted to large bodies than hairy legs," Dr Bussière said. "Our findings suggest that these ornaments may be deceptive rather than honestly indicating female value to males. In other words, the females are seducing the males by inflating their abdominal sacs and positioning their hairy legs in such a way to fool the males into believing they are full of eggs. In turn, the female is rewarded with food."

This work may explain why the focal species has multiple female ornaments, while close relatives have one or none. The scientists concluded that sexual conflict - females deceiving the males so as to increase their chances of obtaining food from mates, and males trying to adapt to protect themselves from being duped by skinnier-than-advertised females - creates diversity among closely related species.

"The angle about deception is the most intriguing one from our perspective," Dr Bussiere continued. "One might have expected the two ornaments work together to create a better signal than either on its own, but the asymmetric importance of the traits to attraction is best explained by conflicts of interest between the sexes.

"We suggest that cycles of evolution could produce a series of ornamental traits in females, as males evolve to resist the deceptive adornments each in turn. Such an explanation would simultaneously explain why females are able to exhibit such elaborate displays - otherwise mostly absent elsewhere in the animal kingdom - and why, in several dance fly species, there are multiple ornaments."

He added: "In order to explain diversity, we have to challenge our understanding of rare cases like this example of female ornamentation, which at first seems to contradict what we know about evolution."
-end-
Dr Jill Wheeler and Professor Darryl Gwynne, both from the University of Toronto, collaborated on the research, Sexual selection on multiple female ornaments in dance flies, which is published in Proceedings of the Royal Society B.

The study was funded by the Natural Sciences and Engineering Research Council of Canada and the University of Stirling.

University of Stirling

Related Species Diversity Articles from Brightsurf:

More plant diversity, less pesticides
Increasing plant diversity enhances the natural control of insect herbivory in grasslands.

New Denisovan DNA expands diversity, history of species
Ancient Denisovan mitochondrial DNA has been recovered in sediments from Baishiya Karst Cave, a limestone cave at the northeast margin of the Tibetan Plateau, 3280 meters above sea level and adds more evidence to the record that Denisovans, a group of extinct hominins that diverged from Neanderthals about 400,000 years ago, may have more widely inhabited northeast central Asia.

Insect diversity boosted by combination of crop diversity and semi-natural habitats
To enhance the number of beneficial insect species in agricultural land, preserving semi-natural habitats and promoting crop diversity are both needed, according to new research published in the British Ecological Society's Journal of Applied of Ecology.

Two new species of parasite discovered in crabs -- discovery will help prevent infection of other marine species
Two new species of parasite, previously unknown to science, have been discovered in crabs in Swansea Bay, Wales, during a study on disease in the Celtic and Irish Seas.

Marine species are outpacing terrestrial species in the race against global warming
Global warming is causing species to search for more temperate environments in which to migrate to, but it is marine species -- according to the latest results of a Franco-American study mainly involving scientists from the CNRS, Ifremer, the Université Toulouse III-Paul Sabatier and the University of Picardy Jules Verne -- that are leading the way by moving up to six times faster towards the poles than their terrestrial congeners.

Ecosystem diversity drives the origin of new shark and ray species
Biologists how different oceanographic conditions in the Gulf of California and the Baja California Peninsula influenced formation of new species of sharks and rays.

One species to four: New analysis documents new bird diversity in the Pacific
New findings from UMBC researchers and colleagues suggest several island bird populations in the Pacific that were previously designated as a single species actually comprise up to four distinct species.

Directed species loss from species-rich forests strongly decreases productivity
At high species richness, directed loss, but not random loss, of tree species strongly decreases forest productivity.

The functional diversity in a noxious heat and chemical sensor among mosquito species
Researchers in the National Institute for Physiological Sciences compared functional properties of TRPA1 which serves as a receptor for noxious heat and chemicals among mosquito species.

DNA exchange among species is major contributor to diversity in Heliconius butterflies
Exchange of genetic material among species played a major role in the wide diversity of Heliconius butterflies, according to a new study, results of which inform a centuries-long debate about the value of hybridization to species evolution.

Read More: Species Diversity News and Species Diversity Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.