Relative Effects of Juvenile and Adult Environmental Factors on Mate Attraction and Recognition in the Cricket, Allonemobius socius

Finding a mate is a fundamental aspect of sexual reproduction. To this end, specific-mate recognition systems (SMRS) have evolved that facilitate copulation between producers of the mating signal and their opposite-sex responders. Environmental variation, however, may compromise the efficiency with which SMRS operate. In this study, the degree to which seasonal climate experienced during juvenile and adult life-cycle stages affects the SMRS of a cricket, Allonemobius socius (Scudder) (Orthoptera: Gryllidae) was assessed. Results from two-choice behavioral trials suggest that adult ambient temperature, along with population and family origins, mediate variation in male mating call, and to a lesser extent directional response of females for those calls. Restricted maximum-likelihood estimates of heritability for male mating call components and for female response to mating call appeared statistically nonsignificant. However, appreciable “maternal genetic effects” suggest that maternal egg provisioning and other indirect maternal determinants of the embryonic environment significantly contributed to variation in male mating call and female response to mating calls. Thus, environmental factors can generate substantial variation in A. socius mating call, and, more importantly, their marginal effect on female responses to either fast-chirp or long-chirp mating calls suggest negative fitness consequences to males producing alternative types of calls. Future studies of sexual selection and SMRS evolution, particularly those focused on hybrid zone dynamics, should take explicit account of the loose concordance between signal producers and responders suggested by the current findings

Elevated Frequency of Cataracts in Birds from Chernobyl

<div><p>Background</p><p>Radiation cataracts develop as a consequence of the effects of ionizing radiation on the development of the lens of the eye with an opaque lens reducing or eliminating the ability to see. Therefore, we would expect cataracts to be associated with reduced fitness in free-living animals.</p><p>Methodology/Principal Findings</p><p>We investigated the incidence of lens opacities typical of cataracts in more than 1100 free-living birds in the Chernobyl region in relation to background radiation. The incidence of cataracts increased with level of background radiation both in analyses based on a dichotomous score and in analyses of continuous scores of intensity of cataracts. The odds ratio per unit change in the regressor was 0.722 (95% CI 0.648, 0.804), which was less than odds ratios from investigations of radiation cataracts in humans. The relatively small odds ratio may be due to increased mortality in birds with cataracts. We found a stronger negative relationship between bird abundance and background radiation when the frequency of cataracts was higher, but also a direct effect of radiation on abundance, suggesting that radiation indirectly affects abundance negatively through an increase in the frequency of cataracts in bird populations, but also through direct effects of radiation on other diseases, food abundance and interactions with other species. There was no increase in incidence of cataracts with increasing age, suggesting that yearlings and older individuals were similarly affected as is typical of radiation cataract.</p><p>Conclusions/Significance</p><p>These findings suggest that cataracts are an under-estimated cause of morbidity in free-living birds and, by inference, other vertebrates in areas contaminated with radioactive materials.</p></div

Mean cataracts in birds from Chernobyl in relation to background radiation level (μSv/h).

<p>The linear fit with confidence intervals is shown.</p

Path analysis of the direct and indirect relationships between cataracts and radiation, respectively, and abundance of breeding birds.

<p><i>U</i> represents the unexplained variance. P-values for path coefficients are * <i>P</i><0.05 and *** <i>P</i><0.001.</p

Relationship between slopes for the relationship between abundance and background radiation and the frequency of cataracts in different species of birds.

<p>The size of symbols reflects variation in sample size.</p

Nominal logistic regression model of cataracts in relation to species and background radiation.

<p><i>R</i>² was 0.21. The odds ratio and its 95% confidence interval is also reported.</p

Mixed model of cataracts in relation to species (random factor) and radiation.

<p>The random species effect accounted for a variance ratio of 0.0955 and 8.71% of the total variance.</p

Photographs of selected eyes from Chernobyl birds.

<p>(a) Blackcap (<i>Sylvia atricapilla</i>), normal – score 0; (b) barred warbler (<i>Sylvia nisoria</i>), normal – score 0; (c) blackcap (<i>Sylvia atricapilla</i>), slight haze in cornea – score 1; (d) barn swallow (<i>Hirundo rustica</i>), significant haze on cornea – score 2; (e) chiffchaff (<i>Phylloscopus collybita</i>), slight haze on cornea – score 1; (f) chiffchaff (<i>Phylloscopus collybita</i>), significant haze on cornea – score 1; (g) barn swallow (<i>Hirundo rustica</i>), significant haze on cornea – score 3; (h) chaffinch (<i>Fringilla coelebs</i>), slight haze on cornea – score 1; (i) chaffinch (<i>Fringilla coelebs</i>), clear eye but deformed eye lids – score 0; (j) tree pipit (<i>Anthus trivialis</i>), significant opacity of cornea – score 2; (k) robin (<i>Erithacus rubecula</i>), significant haze on cornea – score; (l) chiffchaff (<i>Phylloscopus collybita</i>), deformed eye lids, haze on cornea – score 2. All photos captured using an EyeQuick Digital Ophthalmoscope Camera.</p

Evolution of maternal effects: past and present

It has been said that many original ideas reflect a convergence of related thought that coalesces into a unified representation of what many have been thinking. This is certainly true for the subfield of maternal effects evolution. The study of maternal effects has a long history. The first two papers reported in the ISI database dealing with the evolutionary significance of maternal effects were published in Proceedings of the National Academy of Science USA by Dobzhansky & Sturtevant (Dobzhansky 1935, ‘Maternal effect as a cause of the difference between the reciprocal crosses in Drosophila pseudoobscura’; Dobzhansky & Sturtevant 1935, ‘Further data on maternal effects in Drosophila pseudoobscura hybrids’). Surprisingly, given its authors, these papers have received little attention in the literature (a total of 12 citations for the Dobzhansky and Sturtevant paper), perhaps because of their relatively recent addition to electronically searchable databases, although the third paper in the list, by Walton & Hammond (1938), dealing with maternal effects in Shetland ponies, has been well cited (total of 228 citations) with an increasing rate of citation in the past decade. Overall, prior to 1987, ISI reports a total of 185 publications with ‘maternal effects’ as a keyword phrase. Between 1988 and 1997 this number jumped to 520 papers, while from 1998 to the present (November 2008) there have been at least 1397 publications on this topic. These numbers are underestimates, especially for the latter years, as they do not include the many keyword variants of relevant processes (e.g. maternal inheritance, maternal genetic effects, parental effects, epigenetic effects), or papers where the primary emphasis is in a different but related area, but they do reflect a dramatic increase in awareness following the late 1980s of the importance of maternal effects in the evolutionary process