Spatial and temporal population differences in male density and condition in the American rubyspot, Hetaerina americana (Insecta: Calopterygidae) |
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Authors: | Jorge Contreras-Garduño Jorge Canales-Lazcano Jesús Guillermo Jiménez-Cortés Nahum Juárez-Valdez Humberto Lanz-Mendoza Alex Córdoba-Aguilar |
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Institution: | 1. Unidad de Entomología Aplicada, Instituto de Ecología, A. C., Km. 2.5 Ant. Carr. a Coatepec no. 351, Congregación El Haya, 91070, Xalapa, Veracruz, Mexico 2. Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México, Apdo. Postal 70-275, Ciudad Universitaria, 04510, Mexico D.F, Mexico 3. Centro de Investigación Sobre Enfermedades Infecciosas, Instituto Nacional de Salud Pública, Avda. Universidad 655. Col. Sta. María Ahuacatitlán, 62508, Cuernavaca, Morelos, Mexico
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Abstract: | Increased resource availability should favor higher animal density. It may also affect sex ratio, the male condition, and
mating competition over access to females, although the direction of these variables is not straightforward to predict. Using
a non-experimental approach, we carried out preliminary research using the territorial American rubyspot (Hetaerina americana) by comparing two spatially separated populations and the same population in two different seasons (each comparison with
varying population densities). We first compared the sex ratio by counting males (using two categories, territorial and non-territorial)
and females; relative foraging time (as an indicator of how much feeding resources each site provides); wing spot size (a
sexual ornament), body size and immune melanization response (these two variables were used to assess male condition); and
fighting time and contest number (to assess competition). For the seasonal comparison we used a third population in which
we only compared male spot size and two indicators of condition and immune response, phenoloxidase (PO) and nitric oxide (NO)
activity. The high-density population had higher values of non-territorial males (but similar sex ratio), relative foraging
time, contest time and number, wing spot (but similar body size) and melanization response than the low-density population.
According to season, at high density, males had higher values of wing spots, PO, and NO. Our results suggest that in a population
where animals have more dietary resources, males reach a better condition despite the competition being more intense. |
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Keywords: | American rubyspot Density Condition Sex ratio Competition for territories |
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