Our #RacerScholars this week are: Michael P. Moore, Dr. Tobias Landberg, and Dr. Howard H. Whiteman

This week’s #RacerScholars are Michael P. Moore, Dr. Tobias Landberg, and Dr. Howard H. Whiteman from the Watershed Studies Institute at Murray State University. Their paper, “Maternal investment mediates offspring life history variation with context-dependent fitness consequences,” was published in the September 2015 issue of Ecology.

Abstract

Maternal effects, such as per capita maternal investment, often interact with environmental conditions to strongly affect traits expressed early in ontogeny. However, their impact on adult life history traits and fitness components is relatively unknown. Theory predicts that lower per capita maternal investment will have strong fitness costs when the offspring develop in unfavorable conditions, yet few studies have experimentally manipulated per capita maternal investment and followed offspring through adulthood. We used a surgical embryonic yolk removal technique to investigate how per capita maternal investment interacted with an important ecological factor, larval density, to mediate offspring life history traits through reproductive maturity in an amphibian, Ambystoma talpoideum. We predicted that increased larval density would reinforce the life history variation induced by differences in per capita investment (i.e., Controls vs. Reduced Yolk), with Reduced larvae ultimately expressing traits associated with lower fitness than Controls when raised at high densities. We found that Reduced individuals were initially smaller and more developed, caught up in size to Controls within the first month of the larval stage, but were smaller at the end of the larval stage in low densities. Reduced individuals also were more likely to undergo metamorphosis at high densities and mature females invested in more eggs for their body sizes than Controls. Together, our results do not support our hypothesis, but instead indicate that Reduced individuals express traits associated with higher fitness when they develop in high-density environments, but lower fitness in low-density environments. The observed life history and fitness patterns are consistent with the “maternal match” hypothesis, which predicts that when the maternal environment (e.g., high density) results in phenotypic variation that is transmitted to the offspring (e.g., reduced per capita yolk investment), and offspring face that same environment (e.g., high larval density), the fitness of both mother and offspring is maximized.


coverMaternal investment mediates offspring life history variation with context-dependent fitness consequences

By: Michael P. Moore, Tobias Landberg,
and Howard H. Whiteman
Ecology, Sep. 2015, vol. 96 (9), pgs. 2499-2509
doi: 10.1890/14-1602.1

MSU Featured Scholar: Dr. Howard H. Whiteman

Our featured scholar at Murray State University this week is Dr. Howard H. Whiteman, Professor of Biology and Director of the Watershed Studies Institute. Dr. Whiteman co-wrote the article, “Non-additive effects of intra- and interspecific competition between two larval salamanders,” with Murray State alumnus, Thomas L. Anderson. The article appears in the the Journal of Animal Ecology published by the British Ecological Society.

Abstract

Assessment of the relative strengths of intra- and interspecific competition has increased in recent years and is critical to understanding the importance of competition. Yet, whether intra- and interspecific competition can have non-additive effects has rarely been tested. The resulting fitness consequences of such non-additive interactions are important to provide the context necessary to advance our understanding of competition theory. We compared the strength of additive and non-additive intra- and interspecific competition by manipulating densities of a pair of larval salamanders (Ambystoma talpoideum and A.maculatum) in experimental mesocosms within a response surface design. Intraspecific density had the strongest effect on the strength of competition for both species, and few observed comparisons indicated interspecific competition was an important factor in predicting body size, growth or larval period length of either species. Non-additive effects of intra- and interspecific competition influenced some response variables, including size and mass at metamorphosis in A.maculatum, but at a reduced strength compared to intraspecific effects alone. Intraspecific competition was thus the dominant biotic interaction, but non-additive effects also impact the outcome of competition in these species, validating the importance of testing for and incorporating non-additive density effects into competition models.

Journal of Animal EcologyNon-additive effects of intra- and interspecific competition between two larval salamanders
By: Thomas L. Anderson and Dr. Howard H. Whiteman
Journal of Animal Ecology
May 2015, vol. 84(3), pgs. 765–772
doi: 10.1111/1365-2656.12335