Migration in butterflies: a global overview.

Insect populations including butterflies are declining worldwide, and they are becoming an urgent conservation priority in many regions. Understanding which butterfly species migrate is critical to planning for their conservation, because management actions for migrants need to be coordinated across time and space. Yet, while migration appears to be widespread among butterflies, its prevalence, as well as its taxonomic and geographic distribution are poorly understood.

Two centuries of monarch butterfly collections reveal contrasting effects of range expansion and migration loss on wing traits.

Migratory animals exhibit traits that allow them to exploit seasonally variable habitats. In environments where migration is no longer beneficial, such as oceanic islands, migration-association traits may be selected against or be under relaxed selection. Monarch butterflies are best known for their continent-scale migration in North America but have repeatedly become established as nonmigrants in the tropical Americas and on Atlantic and Pacific Islands.

And the beak shall inherit - evolution in response to invasion.

The increased demographic performance of biological invaders may often depend on their escape from specifically adapted enemies. Here we report that native taxa in colonized regions may swiftly evolve to exploit such emancipated exotic species because of selection caused by invaders. A native Australian true bug has expanded it host range to include a vine imported from tropical America that has become a serious environmental weed.

Rapid appearance of epistasis during adaptive divergence following colonization.

Theory predicts that short-term adaptation within populations depends on additive (A) genetic effects, while gene-gene interactions 'epistasis (E)' are important only in long-term evolution. However, few data exist on the genetic architecture of adaptive variation, and the relative importance of A versus non-additive genetic effects continues to be a central controversy of evolutionary biology after more than 70 years of debate. To examine this issue directly, we conducted hybridization experiments between two populations of wild soapberry bugs that have strongly differentiated in 100 or fewer generations following a host plant shift.

GENETIC DIFFERENTIATION OF FITNESS-ASSOCIATED TRAITS AMONG RAPIDLY EVOLVING POPULATIONS OF THE SOAPBERRY BUG.

In this study we used reciprocal rearing experiments to test the hypothesis that there is a genetic basis for the adaptive differences in host-use traits among host-associated soapberry bug populations (described in Carroll and Boyd 1992). These experiments were conducted on two host races from Florida, in which differences in beak length and development were found between natural populations on a native host plant species and those on a recently introduced plant species (colonized mainly post-1950). Performance was generally superior on the host species from which each lab population originated (i.

Geographic variation in embryonic development time and stage of diapause in a grasshopper.

Embryonic development times and the stage at which embryonic diapause occurs varied dramatically among 23 populations of the Melanoplus sanguinipes/ devastator species complex in California, USA. Grasshoppers were collected from a wide range of latitudes (32°57N to 41°20N) and altitudes (10m to 3031 m), spanning much of the variation in climatic conditions experienced by these insects in California. When reared in a "common garden" in the laboratory, total embryonic development times were positively correlated to the mean annual temperature of the habitat from which the grasshoppers were collected (varying from about 19 days to 32 days when reared at 27°C).

Effects of freshwater and marine overwintering environments on life histories of threespine sticklebacks: evidence for adaptive variation between anadromous and resident freshwater populations.

Life history theory predicts that migratory fishes should delay reproduction, be larger at first reproduction, and have higher fecundities than nonmigrants. We tested this hypothesis by comparing life histories of anadromous ("estuary") and resident freshwater ("upstream") threespine sticklebacks (Gasterosteus aculeatus L.) from the Navarro River, California, USA.

Altitudinal variation in life cycle syndromes of California populations of the grasshopper, Melanoplus sanguinipes (F.).

Life cycles of California populations of the grasshopper, Melanoplus sanguinipes, varied along an altitudinal gradient. Temperature records indicate a longer season at low altitude on the coast, based on computation of degree days available for development, even though summer air temperatures are cooler than at high altitude; this is a result of warm soil temperatures. At high and low altitudes there was a high proportion of diapause eggs oviposited, while intermediate proportions of diapause eggs occurred at mid altitudes.

RESPONSES TO SELECTION AMONG LIFE-HISTORY TRAITS IN A NONMIGRATORY POPULATION OF MILKWEED BUGS (ONCOPELTUS FASCIATUS).

Genetic parameters were assessed in the nonmigratory Puerto Rico population of the milkweed bug, Oncopeltus fasciatus, and compared with parameters estimated in a migratory population from Iowa (Palmer and Dingle, 1986). Offspring-parent regression analysis provided initial estimates of heritabilities and phenotypic and genetic correlations among wing length, head-capsule width, female age at first reproduction, fecundity for the first and second five days of reproduction by females, and clutch size for the first and second five days of reproduction by females. Replicated bidirectional selection for wing length was then imposed, with a direct response to selection revealing substantial additive genetic variance for this trait, as was also the case with the Iowa population.

DIRECT AND CORRELATED RESPONSES TO SELECTION AMONG LIFE-HISTORY TRAITS IN MILKWEED BUGS (ONCOPELTUS FASCIATUS).

Offspring-parent regressions provided initial estimates of heritabilities and genetic correlations among wing length, body length, pronotum width, head-capsule width, development time, age at first reproduction, and fecundity in an Iowa population of the large milkweed bug, Oncopeltus fasciatus. Replicated, bidirectional selection for wing length was imposed for nine generations. The direct response to selection revealed the existence of substantial additive genetic variance for wing length in this population.

Geographic variation in the effects of temperature on life-history traits in the large milkweed bug Oncopeltus fasciatus.

Complete sets of life-history data (sufficient to construct life-tables and calculate intrinsic rates of increase) were collected at each of three constant temperatures for descendants of two tropical populations of the Large Milkweed Bug, Oncopeltus fasciatus. Although the two populations occur only about 60 km apart, they experience quite different thermal regimes, with little variation in mean monthly temperature at either site. In addition to the pronounced effect of ambient temperature on life-history traits, significant population-by-temperature interactions were observed for six of the eight traits examined.

The effect of host plant phenology on reproduction of the milkweed bug, Oncopeltus fasciatus, in tropical Florida.

A field study of the relationship between host plant phenology and the reproductive pattern of the large milkweed bug, Oncopeltus fasciatus, was conducted in south Florida. Since O. fasciatus need seeds of either milkweed or Nerium oleander plants to reproduce, reproduction takes place on only those host plants that are producing seed pods.

Competition: Butterflies eliminate milkweed bugs from a Caribbean Island.

By eliminating the food plant, Asclepias curassavica, monarch butterflies, Danaus plexippus, have virtually eliminated milkweed bugs, Oncopeltus spp., from the island of Barbados. The relatively open terrain of Barbados means the plants have no refuge; the butterflies survive on an alternate milkweed food plant, Calotropis procera, whose thick-walled pods make seeds unavailable to the bugs.

Distribution, abundance, and interspecific agonistic behavior of two mudflat stomatopods.

Two species of stomatopod (Fam: Squillidae) were sampled on an intertidal mudflat at Ang Sila on the Gulf of Thailand. In 25 transects each of 23 m we collected 219 Cloridopsis scorpio and 49 Oratosquilla inornata. In interspecific agonistic interactions, both in an open arena and with one animal defending a burrow, C.

Diapause in a migrant insect, the milkweed bug Oncopeltus fasciatus (Dallas) (Hemiptera: Lygaeidae).

Oncopeltus fasciatus exhibits a facultative reproductive diapause which is triggered by short photoperiods. The duration of the triggering photoperiod (the "critical photoperiod") is a function of the environmental conditions under which populations are reared. Some individuals are apparently sensitive to critical photoperiods in the early instars, but maximum sensitivity, indicated by 100% diapause, occurs in the late 5th instar during development of the pharate adult.

Experimental studies of migration in bugs of the genus Dysdercus.

Using a tethered flight technique, migration was studied in the African cotton stainer bugs Dysdercus fasciatus Sign., D. nigrofasciatus Stål, and D.

Interspecific aggressive behavior in tropical reef stomatopods and its possible ecological significance.

Aggressive behavior may play a role in resource partitioning in two Eniwetok stomatopods Gonodactylus incipiens and Haptosquilla glyptocercus. These animals inhabit cavities in coral rubble which they defend vigorously. H.