It has been argued that females should be able to choose parasite-resistant mates on the basis of the quality of male secondary sexual characters and that such signals must be costly handicaps in order to evolve. To a large extent, handicap hypotheses have relied on energetic explanations for these costs. Here, we have presented a phenomenological model, operating on an intraspecific level, which views the cost of secondary sexual development from an endocrinological perspective. The primary androgenic hormone, testosterone, has a dualistic effect; it stimulates development of characteristics used in sexual selection while reducing immu- nocompetence. This "double-edged sword" creates a physiological trade-off that influences and is influenced by parasite burden. We propose a negative-feedback loop between signal intensity and parasite burden by suggesting that testosterone-dependent signal intensity is a plastic re- sponse. This response is modified in accordance with the competing demands of the potential costs of parasite infection versus that of increased reproductive success afforded by exaggerated signals. We clarify how this trade-off is intimately involved in the evolution of secondary sexual characteristics and how it may explain some of the equivocal empirical results that have surfaced in attempts to quantify parasite's effect on sexual selection.

Parasites, bright males, and the immunocompetence handicap

Traditionally, the major biotic determinants of animal community structure were assumed to be competition and predation. Recent theoretical, experimental and field studies indicate that parasitism is also important. The spectrum of effects that parasites have on host individuals is as broad as the range of parasite-host interactions. This review considers evidence for direct effects of parasites on fecundity and survival that influence host demography, and for indirect effects on host physiology and behavior that interface with competition and predation.

https://www.cell.com/trends/ecology-evolution/pdf/0169-5347(91)90071-5.pdf

Parasitism: A cryptic determinant of animal community structure.

Sex biases in parasitism may be expected in mammals because estrogens stimulate immunity, whereas androgens depress immunity. Parasites should, therefore, become more readily established in male hosts, leading to higher levels of parasitism for males than for females. We tested this general hypothesis using 145 tests based on mammal hosts taken from 38 published studies. Male biases in parasitism existed overall and for tests restricted to arthropod (but not helminth) parasites. We then controlled for potential dependence by choosing single parasite species based on their likelihood of eliciting immune responses. For these 48 tests, male biases still existed for arthropod, but not for helminth, parasites. As predicted, the average degree of male bias was much higher for studies involving an experimental infection than for field studies. In experimental tests, researchers controlled for differences between the sexes in exposure to parasites. Any biases in parasitism, therefore, should have been due primarily to gender differences in immune response. There also were no male biases in parasitism among juveniles, presumably because juvenile males and females differ less in their hormone profiles or stress levels than do adult males and females. In , our results suggested that hormonally mediated sex differences in susceptibility to parasitism exist for mammals, even though our tests were extremely conservative. Our results also indicate that, on average, differences in parasitism between the sexes are small, and that statistically significant male biases in parasitism are not a general rule.

https://www.jstor.org/stable/info/3545801

Male biases in parasitism of mammals : effects of study type, host age, and parasite taxon

Physiological capacities may constrain behavioural options and hence have important ecological consequences. We tested the hypothesis that social dominance is related to capacities for locomotor performance in territorial male lizards (Sceloporus occidentalis Baird & Girard). We first measured the maximal sprint speed and stamina of individual lizards in the laboratory. Pairs of size-matched males were then placed into a novel laboratory arena and allowed to compete for access to a basking site under a heat lamp. The lizard that physically controlled the basking site was judged the 'winner' of a dominance interaction (winner vs loser status was confirmed by quantitative scoring of behaviour). Winners of these dyadic encounters had significantly higher sprint speeds in 14 of 20 cases, with winners averaging 16.5% faster than losers. Stamina, however, did not differ between winners and losers. Key-words: Behaviour, dominance, locomotion, performance, speed, stamina

Locomotor Capacity and Social Dominance in Male Lizards

Publisher Summary This chapter discusses on birds and mammals, groups for which the most intensive studies of lekking are available. The current interest in leks arises from the restriction of males' reproductive contributions solely to sperm. This situation distills the complexities of sexual selection. The chapter explains two patterns described repeatedly for lekking birds and mammals: constancy in the locations of leks and nonuniform distributions of matings among males. Then, it examines the behavioral interactions that could produce these patterns. Next, the general evolutionary issues raised by lekking species, including possibilities for sexual selection, and finally to evolutionary scenarios, complex hypotheses for the evolutionary origins of lekking is discussed. In the case of mating systems, including leks, this hierarchical approach separates, in particular, female choice from sexual selection. The first is a behavioral mechanism that can generate patterns of mating between individuals; the second, often a consequence of differences in mating success produced by particular behaviors, is a mechanism of the propagation of genes in a population. In some cases these approaches are conflated and in others pursued almost in isolation.

Lekking in Birds and Mammals: Behavioral and Evolutionary Issues

The effect of malarial parasitism on the ability of male western fence lizards, Sceloporus occidentalis, to compete for access to females was assessed experimentally. Pairs of male lizards, one infected with the malarial parasite, Plasmodium mexicanum, and the other not infected, were matched by size and color and placed in large seminatural outdoor enclosures along with an adult female lizard. Infected males displayed to females and to other males less often than did noninfected male lizards. Noninfected lizards were dominant in social interactions more often than malarious animals, based on duration and intensity of agonistic encounters toward the other male, and time spent with the female. Thus, malarial infection hinders the ability of male fence lizards to compete for mates.

/pdf/malarial-parasitism-and-male-competition-for-mates-in-the-3fzhedg9zh.pdf

Malarial parasitism and male competition for mates in the western fence lizard, Sceloporus occidentalis

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

M. D. Dearing

Author Tools

Chat about Author

Papers

Malarial parasitism and male competition for mates in the western fence lizard, Sceloporus occidentalis