skip to main content


Title: A picture is worth a thousand dollars: a photographic approach to studying colour in anoles
Abstract

Colours relay information to conspecifics and predators unique to an environment and are shaped by natural selection favouring colours that enable higher fitness. For decades, ecologists have grappled with various methods of quantifying colour. Spectrophotometers offer precise and accurate data, but their high price limits accessibility. Here we test the validity of an accessible method of quantifying colour. We analysed photographs from four species of Anolis lizards from urban and forest habitats. We compared dewlap colour in order to determine if photographic analysis can detect inter- and intraspecific differences with the same power as a spectrophotometer. We hypothesized that photographs would capture colour data comparable to a spectrophotometer within the visible light range, and that habitat divergence would be associated with intraspecific differences in dewlap. We demonstrate, as hypothesized, that photographic colour data are consistent with spectrophotometer data and capable of differentiating dewlap variation within the visible light spectrum. Differences in colour between urban and forest populations were significant for some but not all species, and the part of the colour spectrum that shifted was not consistent across species. Our results support photographic analysis as an alternative for quantifying colour to study both inter- and intraspecific variation in visible colour.

 
more » « less
NSF-PAR ID:
10469113
Author(s) / Creator(s):
; ;
Publisher / Repository:
Oxford University Press
Date Published:
Journal Name:
Biological Journal of the Linnean Society
ISSN:
0024-4066
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Cini, Alessandro (Ed.)

    Incoming solar radiation (wavelengths 290–2500 nm) significantly affects an organism’s thermal balance via radiative heat gain. Species adapted to different environments can differ in solar reflectance profiles. We hypothesized that conspecific individuals using thermally distinct microhabitats to engage in fitness-relevant behaviors would show intraspecific differences in reflectance: we predicted individuals that use hot microclimates (where radiative heat gain represents a greater thermoregulatory challenge) would be more reflective across the entire solar spectrum than those using cooler microclimates. Differences in near-infrared (NIR) reflectance (700–2500 nm) are strongly indicative of thermoregulatory adaptation as, unlike differences in visible reflectance (400–700 nm), they are not perceived by ecological or social partners. We tested these predictions in maleCentris pallida(Hymenoptera: Apidae) bees from the Sonoran Desert. MaleC.pallidause alternative reproductive tactics that are associated with distinct microclimates: Large-morph males, with paler visible coloration, behave in an extremely hot microclimate close to the ground, while small-morph males, with a dark brown dorsal coloration, frequently use cooler microclimates above the ground near vegetation. We found that large-morph males had higher reflectance of solar radiation (UV through NIR) resulting in lower solar absorption coefficients. This thermoregulatory adaptation was specific to the dorsal surface, and produced by differences in hair, not cuticle, characteristics. Our results showed that intraspecific variation in behavior, particular in relation to microclimate use, can generate unique thermal adaptations that changes the reflectance of shortwave radiation among individuals within the same population.

     
    more » « less
  2. Abstract

    Understanding variation in key functional traits across gradients in high diversity systems and the ecology of community changes along gradients in these systems is crucial in light of conservation and climate change. We examined inter‐ and intraspecific variation in leaf mass per area (LMA) of sun and shade leaves along a 3330‐m elevation gradient in Peru, and in sun leaves across a forest–savanna vegetation gradient in Brazil. We also comparedLMAvariance ratios (T‐statistics metrics) to null models to explore internal (i.e., abiotic) and environmental filtering on community structure along the gradients. Community‐weightedLMAincreased with decreasing forest cover in Brazil, likely due to increased light availability and water stress, and increased with elevation in Peru, consistent with the leaf economic spectrum strategy expected in colder, less productive environments. A very high species turnover was observed along both environmental gradients, and consequently, the first source of variation inLMAwas species turnover. Variation inLMAat the genus or family levels was greater in Peru than in Brazil. Using dominant trees to examine possible filters on community assembly, we found that in Brazil, internal filtering was strongest in the forest, while environmental filtering was observed in the dry savanna. In Peru, internal filtering was observed along 80% of the gradient, perhaps due to variation in taxa or interspecific competition. Environmental filtering was observed at cloud zone edges and in lowlands, possibly due to water and nutrient availability, respectively. These results related to variation inLMAindicate that biodiversity in species rich tropical assemblages may be structured by differential niche‐based processes. In the future, specific mechanisms generating these patterns of variation in leaf functional traits across tropical environmental gradients should be explored.

     
    more » « less
  3. Abstract

    Climate change is stressing many forests around the globe, yet some tree species may be able to persist through acclimation and adaptation to new environmental conditions. The ability of a tree to acclimate during its lifetime through changes in physiology and functional traits, defined here as its acclimation potential, is not well known.

    We investigated the acclimation potential of trembling aspenPopulus tremuloidesand ponderosa pinePinus ponderosatrees by examining within‐species variation in drought response functional traits across both space and time, and how trait variation influences drought‐induced tree mortality. We measured xylem tension, morphological traits and physiological traits on mature trees in southwestern Colorado, USA across a climate gradient that spanned the distribution limits of each species and 3 years with large differences in climate.

    Trembling aspen functional traits showed high within‐species variation, and osmotic adjustment and carbon isotope discrimination were key determinants for increased drought tolerance in dry sites and in dry years. However, trembling aspen trees at low elevation were pushed past their drought tolerance limit during the severe 2018 drought year, as elevated mortality occurred. Higher specific leaf area during drought was correlated with higher percentages of canopy dieback the following year. Ponderosa pine functional traits showed less within‐species variation, though osmotic adjustment was also a key mechanism for increased drought tolerance. Remarkably, almost all traits varied more year‐to‐year than across elevation in both species.

    Our results shed light on the scope and limits of intraspecific trait variation for mediating drought responses in key southwestern US tree species and will help improve our ability to model and predict forest responses to climate change.

    Read the freePlain Language Summaryfor this article on the Journal blog.

     
    more » « less
  4. Trait-based analyses provide powerful tools for developing a generalizable, physiologically grounded understanding of how forest communities are responding to ongoing environmental changes. Key challenges lie in (1) selecting traits that best characterize the ecological performance of species in the community and (2) determining the degree and importance of intraspecific variability in those traits. Recent studies suggest that globally evident trait correlations (trait dimensions), such as the leaf economic spectrum, may be weak or absent at local scales. Moreover, trait-based analyses that utilize a mean value to represent a species may be misleading. Mean trait values are particularly problematic if species trait value rankings change along environmental gradients, resulting in species trait crossover. To assess how plant traits (1) covary at local spatial scales, (2) vary across the dominant environmental gradients, and (3) can be partitioned within and across taxa, we collected data on 9 traits for 13 tree species spanning the montane temperate—boreal forest ecotones of New York and northern New England. The primary dimension of the trait ordination was the leaf economic spectrum, with trait variability among species largely driven by differences between deciduous angiosperms and evergreen gymnosperms. A second dimension was related to variability in nitrogen to phosphorous levels and stem specific density. Levels of intraspecific trait variability differed considerably among traits, and was related to variation in light, climate, and tree developmental stage. However, trait rankings across species were generally conserved across these gradients and there was little evidence of species crossover. The persistence of the leaf economics spectrum in both temperate and high-elevation conifer forests suggests that ecological strategies of tree species are associated with trade-offs between resource acquisition and tolerance, and may be quantified with relatively few traits. Furthermore, the assumption that species may be represented with a single trait value may be warranted for some trait-based analyses provided traits were measured under similar light levels and climate conditions. 
    more » « less
  5. PREMISE

    Environmental heterogeneity influences plant distributions and diversity at several spatial scales. In temperate forests, fine‐scale environmental variation may promote local coexistence among herbaceous species by allowing plants to spatially partition microsites within forest stands. Here we argue that shallow soils, low soil water‐holding capacity and fertility, and reduced light near tree boles should favor short, shallow‐rooted, evergreen species likeAnemone acutilobawith low moisture, nutrient, and light requirements. Farther from trees, richer, deeper soils should favor taller, deeper‐rooted herbs with greater moisture and nutrient demands, such asSanguinaria canadensisandTrillium flexipes.

    METHODS

    We tested these hypotheses by mapping the fine‐scale distributions ofAnemone,Sanguinaria, andTrilliumindividuals within a 50 × 50 m plot, comparing local species’ distributions with respect to soil depth and proximity to neighboring trees, and characterizing intraspecific and interspecific spatial associations.

    RESULTS

    Local plant distributions were consistent with our predictions based on leaf height, physiology, and phenology.Anemonewas found in microsites on shallower soils and closer to trees than eitherSanguinariaorTrillium. In all three species, individual plants were spatially aggregated within 2 m, but spatially segregated from individuals of the other species beyond 2 m.

    CONCLUSIONS

    Differential plant responses to fine‐scale environmental heterogeneity and observed spatial associations suggest that local species‐environment associations could facilitate coexistence. These findings illustrate how fine‐scale environmental heterogeneity coupled with phenological and physiological differences likely contribute to spatial niche partitioning among spring‐flowering forest herbs and maintain high local plant diversity within temperate forests.

     
    more » « less