▪ Abstract The latitudinal gradient of decreasing richness from tropical to extratropical areas is ecology's longest recognized pattern. Nonetheless, notable exceptions to the general pattern exist, and it is well recognized that patterns may be dependent on characteristics of spatial scale and taxonomic hierarchy. We conducted an extensive survey of the literature and provide a synthetic assessment of the degree to which variation in patterns (positive linear, negative linear, modal, or nonsignificant) is a consequence of characteristics of scale (extent or focus) or taxon. In addition, we considered latitudinal gradients with respect to generic and familial richness, as well as species evenness and diversity. We provide a classification of the over 30 hypotheses advanced to account for the latitudinal gradient, and we discuss seven hypotheses with most promise for advancing ecological, biogeographic, and evolutionary understanding. We conclude with a forward-looking synthesis and list of fertile areas f...

LATITUDINAL GRADIENTS OF BIODIVERSITY:Pattern,Process,Scale,and Synthesis

It is clear that the above can lead to confusion when scientists of different countries are trying to communicate with each other. Another example is the burrowing rodent called a gopher found throughout the western United States. In the southeastern United States the term gopher refers to a burrowing turtle very similar to the desert tortoise found in the American southwest. One final example; two North American mammals known as the elk and the caribou are known in Europe as the reindeer and the elk. We never sing “Rudolph the Red-nosed elk”! Confused? This was the reason for creating an internationally recognized system of naming organisms. To avoid confusion, living organisms are assigned a scientific name based on Latin or Latinized words. The English sparrow is Passer domesticus or Passer domesticus (italics or underlining these two names is the official written representation of a scientific name). Using a uniform naming system allows scientists from all over the world to recognize exactly which life form a scientist is referring to. The naming process is called the binomial system of nomenclature. Passer is comparable to a surname and is called the genus, while domesticus is the specific or species name (like your given name) of the English sparrow. Now scientists can give all sparrow-like birds the genus Passer but the species name will vary. All similar genera (plural for genus) can be grouped into another, “higher” category (see below). Study the following for a more through understanding of taxonomy. Taxonomy Analogy Kingdom: Animalia Country

Diversity of life

Broad-scale variation in taxonomic richness is strongly correlated with climate. Many mechanisms have been hypothesized to explain these patterns; however, testable predictions that would distinguish among them have rarely been derived. Here, we examine several prominent hypotheses for climate–richness relationships, deriving and testing predictions based on their hypothesized mechanisms. The ‘energy–richness hypothesis’ (also called the ‘more individuals hypothesis’) postulates that more productive areas have more individuals and therefore more species. More productive areas do often have more species, but extant data are not consistent with the expected causal relationship from energy to numbers of individuals to numbers of species. We reject the energy–richness hypothesis in its standard form and consider some proposed modifications. The ‘physiological tolerance hypothesis’ postulates that richness varies according to the tolerances of individual species for different sets of climatic conditions. This hypothesis predicts that more combinations of physiological parameters can survive under warm and wet than cold or dry conditions. Data are qualitatively consistent with this prediction, but are inconsistent with the prediction that species should fill climatically suitable areas. Finally, the ‘speciation rate hypothesis’ postulates that speciation rates should vary with climate, due either to faster evolutionary rates or stronger biotic interactions increasing the opportunity for evolutionary diversification in some regions. The biotic interactions mechanism also has the potential to amplify shallower, underlying gradients in richness. Tests of speciation rate hypotheses are few (to date), and their results are mixed.

Predictions and tests of climate‐based hypotheses of broad‐scale variation in taxonomic richness

Broad-scale variation in taxonomic richness is strongly correlated with climate. Many mechanisms have been hypothesized to explain these patterns; however, testable predictions that would distinguish among them have rarely been derived. Here, we examine several prominent hypotheses for climate–richness relationships, deriving and testing predictions based on their hypothesized mechanisms. The energy–richness hypothesis (also called the more individuals hypothesis ) postulates that more productive areas have more individuals and therefore more species. More productive areas do often have more species, but extant data are not consistent with the expected causal relationship from energy to numbers of individuals to numbers of species. We reject the energy–richness hypothesis in its standard form and consider some proposed modifications. The physiological tolerance hypothesis postulates that richness varies according to the tolerances of individual species for different sets of climatic conditions. This hypothesis predicts that more combinations of physiological parameters can survive under warm and wet than cold or dry conditions. Data are qualitatively consistent with this prediction, but are inconsistent with the prediction that species should fill climatically suitable areas. Finally, the speciation rate hypothesis postulates that speciation rates should vary with climate, due either to faster evolutionary rates or stronger biotic interactions increasing the opportunity for evolutionary diversification in some regions. The biotic interactions mechanism also has the potential to amplify shallower, underlying gradients in richness. Tests of speciation rate hypotheses are few (to date), and their results are mixed.

PERSPECTIVES Predictions and tests of climate-based hypotheses of broad-scale variation in taxonomic richness

Recapitulation des determinants ecologiques, genetiques et comportementaux du comportement d'oviposition chez diverses mouches. Evaluation de l'influence de ce comportement sur l'evolution du choix de l'hote

Evolution of Oviposition Behavior and Host Preference in Lepidoptera

The Nature Handbook

. Fourteen populations of the montane butterfly E. gillettii Barnes were surveyed initially during 1982–1984 and again during 2002–2006 to assess reasons for decline, extirpation, and colonization. Surveys were conducted by counting egg masses at each site soon after the flight period. Seven of the 14 populations disappeared between the two surveys because of vegetative succession, drying of meadow habitats, and isolation from other colonies. Populations at low elevations and low latitude were more likely to die out; colonies that were part of a metapopulation were more likely to survive. One population reestablished at a high elevation site where the habitat remained moist. The vegetation had changed conspicuously at all sites where the butterflies were extirpated, with climate change being implicated in the drying of the habitats. Given the modest number of known populations, continued attention to the status of the species is warranted.

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Population Loss and Gain in the Rare Butterfly Euphydryas gillettii (Nymphalidae)

. One response of living organisms to a changing climate is a shift in phenology; ectotherms in particular are apt to appear earlier under warmer conditions. We have used citizen science data collected by the Massachusetts Butterfly Club to measure the rates of phenological advance by ten species of univoltine lycaenid butterflies, including five spring emergent elfins (Callophrys spp.) and five summer emergent hairstreaks (Satyrium spp.). We ran regression analyses separately on all observational data and on the first 20 percent of observations and evaluated both data sets with equal sampling over time. We found that Massachusetts had warmed over the 27 year period of study, with April having the highest rate of warming; that all 10 lycaenid species are appearing earlier in the spring and summer than they used to; that spring-emergent elfins have shown a greater response to warming (4.8 days/ °C) than summer-emergent hairstreaks (3.1 days/ °C); that as a group elfins advanced 14.2 days in initial...

Phenological Advancement of Lycaenid Butterflies in Massachusetts

This study assessed the influence of annual snowpack on long term changes in the predatory regime of four high elevation ponds in the mountains of northwest Wyoming. Over 36 y of observation, in two ponds the primary predator alternated between phantom midge Chaoborus americanus larvae and Diaptomus shoshone predatory copepods, whereas the predatory regime did not change in the other two shallower ponds. Switching of predators correlated with extreme amounts of winter snow, either high or low, which determined the depth at which drying or complete freezing of the pond occurred. Chaoborus americanus colonized ponds after the wettest years and disappeared after the driest years. The results provide an unusual long term perspective of the effects of weather on predator dominance.

Ernest H. Williams

Papers

The Nature Handbook

Population Loss and Gain in the Rare Butterfly Euphydryas gillettii (Nymphalidae)

Phenological Advancement of Lycaenid Butterflies in Massachusetts

Long Term Effects of Climate on Two Pond Predators

The Nature Handbook: A Guide to Observing the Great Outdoors