Niche Partitioning between Two Sympatric Lizards in the Chiricahua Mountains of Arizona
Competition for resources between sympatric species can result in reduced fitness. Resource partitioning allows the minimization of competitive pressures, consequently promoting the coexistence of a diversity of species. We tested the hypothesis that the Striped Plateau Lizard (Sceloporus virgatus) and the Ornate Tree Lizard (Urosaurus ornatus) that occur in sympatry in the Chiricahua mountains of Arizona, USA have distinct ecological niches to minimize interspecific competition. We compared the activity times, perch microhabitat characteristics, and diet of these insectivorous lizards to test the prediction that they partition resources. Although we found no difference between the two species in the time at which lizards become active in the morning nor in the composition of their diets, the two species used different structural perch microhabitats. The Ornate Tree Lizard selected higher and narrower perches with more closed canopy than the Striped Plateau Lizard, and males generally occupied higher perches than females. These differences in perch microhabitat use may reduce interspecific competition and allow these two sympatric species to cohabitate.
Proportional use of each substrate type (log, rock, and tree) differed between Urosaurus ornatus and Sceloporus virgatus in the upland habitat, but did not differ in the wash habitat nor between sexes within each species in the Chiricahua Mountains of Arizona, USA.
Canopy cover at perching sites differed between Urosaurus ornatus and Sceloporus virgatus in both habitat types (upland and wash), but not between sexes, in the Chiricahua Mountains of Arizona, USA. The boxes span the interquartile range (from the 25th percentile to the 75th percentile) with the horizontal line within each box representing the median (50th percentile), whilst the whiskers extend to the lowest and highest observations excluding outliers.
Perch height differed significantly between Urosaurus ornatus and Sceloporus virgatus as well as between sexes in both habitat types (upland and wash) in the Chiricahua Mountains of Arizona, USA. The boxes span the interquartile range (from the 25th percentile to the 75th percentile) with the horizontal line within each box representing the median (50th percentile), whilst the whiskers extend to the lowest and highest observations excluding outliers.
Perch width differed significantly between Urosaurus ornatus and Sceloporus virgatus in both habitat types (upland and wash), but not between sexes, in the Chiricahua Mountains of Arizona, USA. The boxes span the interquartile range (from the 25th percentile to the 75th percentile) with the horizontal line within each box representing the median (50th percentile), whilst the whiskers extend to the lowest and highest observations excluding outliers.
5th percentile of the time at which the first individual was observed daily did not differ between Urosaurus ornatus and Sceloporus virgatus or habitat types (upland and wash) in the Chiricahua Mountains of Arizona, USA. The boxes span the interquartile range (from the 25th percentile to the 75th percentile) with the horizontal line within each box representing the median (50th percentile), whilst the whiskers extend to the lowest and highest observations excluding outliers.
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