Showing papers by "Lincoln P. Brower published in 2009"

The Influence of Eastern North American Autumnal Migrant Monarch Butterflies ( Danaus plexippus L.) on Continuously Breeding Resident Monarch Populations in Southern Florida

Abstract: In Florida, the eastern North American population of the monarch butterfly exhibits geographic variability in population structure and dynamics. This includes the occurrence of migrants throughout the peninsula during the autumnal migration, occasional overwintering clusters that form along the Gulf Coast, remigrants from Mexico that breed in north-central Florida during the spring, and what have been assumed to be year-round, resident breeding populations in southern Florida. The work reported here focused on two monarch populations west of Miami and addressed four questions: Are there permanent resident populations of monarchs in southern Florida? Do these breed continuously throughout the year? Do they receive northern monarchs moving south during the autumn migration? Do they receive overwintered monarchs returning via Cuba or the Yucatan during the spring remigration from the Mexican overwintering area? Monthly collections and counts of spermatophores in the bursa copulatrices of females established that a resident population of continuously breeding monarchs exists year-round in southern Florida. It was determined through cardenolide fingerprinting that most of the butterflies had bred on the local southern Florida milkweed species, Asclepias curassavica. During the autumn migration period, however, some monarchs had fed on the northern milkweed, Asclepias syriaca. It appears that instead of migrating to Mexico, these individuals travel south through peninsular Florida, break diapause, mate with and become incorporated into the resident breeding populations. None of the monarchs captured in spring had the A. syriaca cardenolide fingerprint, which is evidence against the southern Florida populations receiving overwintered remigrants from Cuba, Central America or Mexico.

Oyamel fir forest trunks provide thermal advantages for overwintering monarch butterflies in Mexico

Abstract: Survivalofoverwinteringmonarchbutterfliesfollowingseverewetwin- terstormsinMexicoissubstantiallyhigherforbutterfliesthatformclustersontheoya- melfirtreetrunksthanforthosethatformclustersonthefirboughs. 2. Thermal measurements taken at similar elevations with a weather station on the SierraChincuaandwithinaCerroPelonandaSierraChincuaoverwinteringareaindicated thatclusteringonthefirtrunksprovidesdualmicroclimaticbenefitsforthebutterflies. a. At night, the minimum surface temperatures of all firs combined averaged 1.4 ! C warmer than ambient forest temperatures, thereby enhancing protection against freezing formonarchsthatareeitherwetordry.Wetermthisthe'hotwaterbottleeffect.' b. During the day, the maximum surface temperatures of all firs combined averaged 1.2! Ccoolerthanambient,adifferencesufficienttolowerthelossofthebutterflies'lipid storesoverthe154-daywinteringseason. 3. Larger diameter trees increase both microclimate benefits. 4. Theresultsaddanewdimensiontoimprovingtheconservationmanagementguide- lines for the Monarch Butterfly Biosphere Reserve. Strict enforcement against culling of largertreesandinfavourofpromotingold-growthoyamelforestswillenhancetwomicro- climatic benefits: butterfly mortality during severe winterweatherwill be reduced, and the butterflies'lipidsavingsoverthewinterwillbeenhanced.

Chapter 171 – Monarchs

Abstract: Publisher Summary This chapter focuses on the monarch butterfly (Danaus plexippus, Nymphalidae), which belongs to the tropical subfamily Danainae, the members of which are called milkweed butterflies because their larval host plants occur mainly in the milkweed family, Asclepiadaceae. With the exception of the monarch, most of the 157 known Danainae species are limited to tropical regions in Malaysia, Africa, South America, and the Greater Antilles. The adults of several species exhibit both short-distance migrations during the dry and wet seasons and social clustering behavior. This suggests that the long-distance migration and overwintering-aggregation behavior of the monarch butterfly in North America was evolutionarily elaborated from an ancient (plesiomorphic) character of the taxon. During the late Cenozoic, the milkweed genus Asclepias underwent an adaptive radiation that produced 108 species in temperate North America, ranging from Mexico to the boreal forests of Canada and from the Atlantic to the Pacific coasts. As the climate alternated between hot and cold periods during the Pleistocene, the North American flora periodically advanced and retreated. The author hypothesizes that the monarch tracked the geographic expansion and retraction of its milkweed hosts and in the process refined its inherited ancestral ability to move between habitats. Because the monarch cannot tolerate temperate zone winters, natural selection would have favored those individuals that moved southward as summer waned. As time passed, the migration syndrome gradually evolved to become increasingly sophisticated, ending in the present round-trip.