Header

UZH-Logo

Maintenance Infos

Selection on morphological traits and fluctuating asymmetry by a fungal parasite in the yellow dung fly


Blanckenhorn, Wolf U (2017). Selection on morphological traits and fluctuating asymmetry by a fungal parasite in the yellow dung fly. bioRxiv 136325, University of Zurich.

Abstract

A Preprint reviewed and recommended by Peer Community Evolutionary Biology: http://dx.doi.org/10.24072/pci.evolbiol.100027 Evidence for selective disadvantages of large body size remains scarce in general. Previous phenomenological studies of the yellow dung fly Scathophaga stercoraria have demonstrated strong positive sexual and fecundity selection on male and female size. Nevertheless, the body size of flies from a Swiss study population has declined by almost 10% from 1993 to 2009. Given substantial heritability of body size, this negative evolutionary response of an evidently positively selected trait suggests important selective factors being missed (e.g. size-selective predation or parasitism). A periodic epidemic outbreak of the fungus Entomophthora scatophagae allowed assessment of selection exerted by this parasite fatal to adult flies. Fungal infection varied over the season from ca. 50% in the cooler and more humid spring and autumn to almost 0% in summer. The probability of dying from fungal infection increased with adult body size. All infected females died before laying eggs, so there was no fungus impact on female fecundity beyond its impact on mortality. Large males showed the typical mating advantage in the field, but this pattern of positive sexual selection was nullified by fungal infection. Mean fluctuating asymmetry of paired appendages (legs, wings) did not affect the viability, fecundity or mating success of yellow dung flies in the field. This study demonstrates rare parasite-mediated disadvantages of large adult body size in the field. Reduced ability to combat parasites such as Entomophthora may be an immunity cost of large size in dung flies, although the hypothesized trade-off between fluctuating asymmetry, a presumed indicator of developmental instability and environmental stress, and immunocompetence was not found here.

Abstract

A Preprint reviewed and recommended by Peer Community Evolutionary Biology: http://dx.doi.org/10.24072/pci.evolbiol.100027 Evidence for selective disadvantages of large body size remains scarce in general. Previous phenomenological studies of the yellow dung fly Scathophaga stercoraria have demonstrated strong positive sexual and fecundity selection on male and female size. Nevertheless, the body size of flies from a Swiss study population has declined by almost 10% from 1993 to 2009. Given substantial heritability of body size, this negative evolutionary response of an evidently positively selected trait suggests important selective factors being missed (e.g. size-selective predation or parasitism). A periodic epidemic outbreak of the fungus Entomophthora scatophagae allowed assessment of selection exerted by this parasite fatal to adult flies. Fungal infection varied over the season from ca. 50% in the cooler and more humid spring and autumn to almost 0% in summer. The probability of dying from fungal infection increased with adult body size. All infected females died before laying eggs, so there was no fungus impact on female fecundity beyond its impact on mortality. Large males showed the typical mating advantage in the field, but this pattern of positive sexual selection was nullified by fungal infection. Mean fluctuating asymmetry of paired appendages (legs, wings) did not affect the viability, fecundity or mating success of yellow dung flies in the field. This study demonstrates rare parasite-mediated disadvantages of large adult body size in the field. Reduced ability to combat parasites such as Entomophthora may be an immunity cost of large size in dung flies, although the hypothesized trade-off between fluctuating asymmetry, a presumed indicator of developmental instability and environmental stress, and immunocompetence was not found here.

Statistics

Citations

Dimensions.ai Metrics

Altmetrics

Downloads

6 downloads since deposited on 15 Feb 2018
6 downloads since 12 months
Detailed statistics

Additional indexing

Item Type:Working Paper
Communities & Collections:07 Faculty of Science > Institute of Evolutionary Biology and Environmental Studies
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Language:English
Date:2017
Deposited On:15 Feb 2018 10:31
Last Modified:30 Jul 2018 06:53
Series Name:bioRxiv
OA Status:Hybrid
Free access at:Official URL. An embargo period may apply.
Publisher DOI:https://doi.org/10.1101/136325
Official URL:https://www.biorxiv.org/content/early/2018/01/11/136325

Download

Download PDF  'Selection on morphological traits and fluctuating asymmetry by a fungal parasite in the yellow dung fly'.
Preview
Content: Published Version
Filetype: PDF
Size: 2MB
View at publisher