▪ 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

During the 2009-2010 overwintering season and following a 15-year downward trend, the total area in Mexico occupied by the eastern North American population of overwintering monarch butterflies reached an all-time low. Despite an increase, it remained low in 2010-2011. 2. Although the data set is small, the decline in abundance is statistically signifi- cant using both linear and exponential regression models. 3. Three factors appear to have contributed to reduce monarch abundance: degra- dation of the forest in the overwintering areas; the loss of breeding habitat in the Uni- ted States due to the expansion of GM herbicide-resistant crops, with consequent loss of milkweed host plants, as well as continued land development; and severe weather. 4. This decline calls into question the long-term survival of the monarchs' migra- tory phenomenon. Resumen. 1. Durante la temporada invernal 2009-2010, y siguiendo una tenden- cia a la baja de 15 anos, la superficie total ocupada por mariposas monarca en Mexico, provenientes del este America del Norte, llegoa su punto mas bajo. A pesar de su incremento, dicha superficie siguiosiendo baja en 2010-2011. 2. Aunque que el conjunto de datos disponibles es aun pequeno, esta disminucion de la abundancia de mariposas es estadisticamente significativa, tanto si se usan modelos de regresion lineales como exponenciales. 3. Hay tres factores que parecen haber contribuido con esta tendencia de reduc- ciond el numero de mariposas: la degradacion de bosque en las areas de invernacion en Mexico; la perdida de habitat de reproduccion en los Estados Unidos, debido a la expansiond e cultivos geneticamente modificados resistentes a herbicidas, con la consiguiente perdida de las plantas hospederas de algodoncillo, y por continuos cambios en el uso del suelo no favorables para ellas; y, las recientes condiciones cli- maticas severas. 4. Esta disminucion hace que nos cuestionemos sobre la posibilidad de superviven- cia a largo plazo del fenomeno migratorio de las mariposas monarca.

/pdf/decline-of-monarch-butterflies-overwintering-in-mexico-is-efscjptikg.pdf

Decline of monarch butterflies overwintering in Mexico: is the migratory phenomenon at risk?

Aim

We used data from the annual Fourth of July Butterfly Count for the years 1989–97 to examine patterns of species richness and total butterfly abundance across North America and within topographically diverse and disturbed landscapes.



Location

We analysed counts from 514 different locations in North America. The counts represent all areas of the USA and southern Canada, with a few Mexican sites as well, although most counts were in the eastern USA.



Methods

First, we standardized published count data according to the effort expended per count (total party-hours). Using regression analysis and analysis of variance, we then examined the impact of latitude, longitude, topographical relief, habitat disturbance and different climatic measures on the species richness and total abundance of butterflies per count. We also examined the abundance of exotic species in disturbed landscapes.



Results

Our analyses suggest that: (1) species richness is highest at low latitudes and near Rocky Mountain longitudes; (2) the total abundance of individuals is highest in northern US latitudes and Great Plains longitudes; (3) species richness but not total abundance increases with greater topographical relief; (4) species richness and diversity indices are lower in more disturbed habitats; and (5) the abundance of the introduced Pieris rapae (L.) is greater in more disturbed habitats.



Main conclusions

Different factors control the abundance and species richness of North American butterflies. Along with geographical location, habitat disturbance and topographical variability affect species richness. Our analysis also shows the value of broad-based monitoring regimes, such as the North American Fourth of July Butterfly Count.

https://www.jstor.org/stable/pdfplus/2656280.pdf

The diversity and abundance of North American butterflies vary with habitat disturbance and geography

Euphydryas gillettii in a montane meadow in Wyoming oviposits in clusters on the highest large leaves of its larval host, the shrub Lonicera involucrata. Egg masses are found on the underside of leaves which predominantly face the southeast and thereby intercept morning sun. Measurements of leaf temperatures show that, during the cool, clear mornings, these leaves are warmer than leaves of the opposite orientation. Manipulative experiments demonstrate that eggs on these slightly warmer microsites hatch significantly faster than eggs on leaves of other orientations. Because of the rapid onset of winter, an increased developmental rate is likely to correlate directly with increased fitness. The proximal mechanism yielding such a result may be that females choose oviposition sites in the shade.

Thermal influences on oviposition in the montane butterfly Euphydryas gillettii.

http://www.concordmuseum.org/assets/PolgarButterflies.pdf

Climate effects on the flight period of Lycaenid butterflies in Massachusetts

To determine if manipulation of milkweed's natural phenology would increase monarch reproduction, strips were mowed in fields in upstate New York in early Jul., late Jul., and mid Aug., 2006, for comparison to an unmowed control. Common milkweed (Asclepias syriaca) was then monitored from Jul. 29 through Sep. 24 for plant height, vegetative stage, level of herbivory, condition, monarch eggs and larvae, and the position of eggs on leaves and stems. We found mowing on Jul. 1 and 24 spurred the regrowth of milkweed and sustained a more continuously suitable habitat for monarch oviposition and larval development than the control. Mowing on Aug. 17 proved too late for recovery of the milkweeds. Significantly more eggs were laid on the fresh resprouted milkweeds than on the older and taller control plants. In the strips mowed on Jul. 1, peak egg densities occurred in late Jul.; in the strips mowed in late Jul., peak egg densities occurred in early to mid Aug. Depending on the timing of mowing, the milkweed plant height, developmental stage, and condition differed. As predicted, the mowing of fields with Asclepias syriaca extended the monarchs' breeding season and increased overall monarch reproduction. However, timing of mowing was critical and must be determined empirically for different milkweed species and in different locations. This mitigation procedure could be fostered along roadsides, along edges of fields and pastures, in USDA conservation reserve program lands, and along power lines and other rights of way.

https://bioone.org/journals/The-American-Midland-Naturalist/volume-173/issue-2/amid-173-02-229-240.1/Enhancing-Monarch-Butterfly-Reproduction-by-Mowing-Fields-of-Common-Milkweed/10.1674/amid-173-02-229-240.1.pdf

Ernest H. Williams

Papers

Decline of monarch butterflies overwintering in Mexico: is the migratory phenomenon at risk?

The diversity and abundance of North American butterflies vary with habitat disturbance and geography

Thermal influences on oviposition in the montane butterfly Euphydryas gillettii.

Climate effects on the flight period of Lycaenid butterflies in Massachusetts

Enhancing Monarch Butterfly Reproduction by Mowing Fields of Common Milkweed