Abstract
Heterogeneity in resource availability and quality can trigger spatial patterns in the expression of sexually selected traits such as body mass and weaponry. While relationships between habitat features and phenotypic quality are well established at broad geographical scales, information is poor on spatial patterns at finer, intrapopulation scales. We analyzed biometric data collected on 1965 red deer Cervus elaphus males over 20 years from a nonmigratory population living on two sides of a mountainous ridge, with substantial differences in land cover and habitat quality but similar climate and population density. We investigate spatial patterns in (i) body mass, (ii) antler mass, and (iii) antler investment. We also tested for site‐ and age‐specific patterns in allometric relationship between body mass and antler mass. Statistically significant fine‐scale spatial variations in body mass, antler mass, and, to a lesser extent, antler allocation matched spatial differences in land cover. All three traits were greater in the northern slope, characterized by higher habitat heterogeneity and greater availability of open habitats, than in the southern slope. Moreover, the allometric relationship between body mass and antler mass differed among age‐classes, in a pattern that was consistent between the two mountain slopes. Our results support the occurrence of spatial patterns in the expression of individual attributes also at a fine, intrapopulation scale. Our findings emphasize the role of environmental heterogeneity in shaping spatial variations of key life‐history traits, with potential consequences for reproductive success.
Highlights
Spatial variation of environmental factors has a major influence on several ecological processes affecting individuals and populations (e.g., Cromsigt et al, 2009; Karanth et al, 2004; Post et al, 2009)
A strong allometric relationship has been reported between antler mass and eviscerated body mass in adult red deer of different populations (Huxley, 1931)
Districtk ∼ N(0, 2District) where ijk was the expected value of the response variable for measure i in hunting year j and hunting district k, f the smoothing term for age by site selected via cross-validation (Wood, 2017), and the dispersion parameter estimated from the data
Summary
Spatial variation of environmental factors has a major influence on several ecological processes affecting individuals and populations (e.g., Cromsigt et al, 2009; Karanth et al, 2004; Post et al, 2009). Spatial variation of abundance of key resources would be predicted to elicit spatial patterns of investment on traits such as male horns or antlers Given their wide distribution range encompassing a variety of landscapes, and large inter-and intraspecific variation in body mass, male cervids are suitable to investigate spatial correlates of individual allocation to sexually selected secondary traits (Geist, 1998). A strong allometric relationship has been reported between antler mass and eviscerated body mass in adult red deer of different populations (Huxley, 1931) This “positive allometry” is often associated with the growth of conspicuous secondary sexual traits (Kodric- Brown et al, 2006; O’Brien et al, 2018). We predicted that allometric relationship will vary among age-classes, possibly increasing with age (Schröder, 1983) and will be weaker in the less productive site (Jones et al, 2018)
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