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Frans_Jozef
Sunday, May 14th, 2006, 03:38 PM
Dispersal of butterflies in human-altered landscapes – a study of two common grassland species in the agricultural landscape of Scania, southern Sweden

Stefan Gödderz

ABSTRACT

In this study I explored the effects of habitat fragmentation on common butterfly species, in particular focusing on whether ecological characteristics of these butterflies affected the consequences of habitat fragmentation. Thus, the aim was to understand if the change in the modern agricultural landscape might affect the persistence of spatially subdivided populations of butterflies. I conducted this study in agricultural landscape with fragmented grassland habitats in order to investigate if landscape constrains movement of common butterflies and potentially affects population viability and gene-flow.

This question I approached with a direct method (mark-recapture study) and an indirect method (AFLP) to estimate dispersal. Both methods supplement each other: Mark-recapture studies tend to underestimate dispersal, which can be compensated by measuring the proportion of exchange of individuals over larger distances by the use of molecular methods. Mark-recapture data revealed different dispersal patterns for C. pamphilus and L. phlaeas. The dispersal capacity might be altered by the way the butterflies perceive the habitat fragmentation and how matrix resistance is created. However, butterflies are differently affected by habitat fragmentation.

This study was able to show those differences although the mechanisms that create matrix resistance are not fully understood but worth to be investigated. My estimations from the mark-recapture study, as expected, confirmed by analysing population subdivision. Genetic differentiation was rather weak for C. pamphilus, confirming its good mobility. L. phlaeas with lower dispersal capacity showed limited gene-flow, which resulted in a low to moderate population subdivision. I found that dispersal was likely to be more successful in continuous habitat than in fragmented habitat. C. pamphilus and L. phlaeas were affected negatively in their dispersal patterns by the matrix. C. pamphilus was affected less strong than L. phlaeas. However, these two species responded differently to habitat fragmentation. The interpretation of results concerning the biology of butterflies, especially regarding spatial aspects, relays essentially on the knowledge of the species’ mobility and how this changes with a changing environment.

http://www-naturvardskedjan.slu.se/documents/publikationer/godderzthesis.pdf

Liberator Germaniae
Friday, March 23rd, 2007, 11:18 PM
Although the following article is only vaguely related to this thread, I decided to post it here rather than opening a new thread. This is encouraging news indeed!


Taiwan to block highway for butterfly migration

Taipei, Taiwan

23 March 2007 05:18

Taiwan will cordon off part of a highway to facilitate the annual migration of the purple butterfly, whose immigration is compared to that of the monarch butterfly in Mexico, an official said on Friday.

From March 26 to April 6, highway authorities are scheduled to close off the outer lanes of the Number Three highway in west Taiwan, to prevent the butterflies from being hit and killed by passing cars when they fly over the highway during their south-north migration, Taiwan Highway Bureau director Lee Tai-ming told reporters.

The bureau is also to erect mess nets on the side of the highway to make the purple butterflies fly higher when they cross the highway, and to install ultraviolet lights to guide them to cross the highway under a highway bridge.

This is the first time the Taiwanese government has taken steps to protect the migration of the purple butterfly, which is found only in Taiwan and whose annual migration has puzzled scientists.

"This is very necessary, because after spending the winter in the mountain valley, the purple butterflies are thin and weak, and can be easily killed by passing cars," said Chan Chia-long, head of the Taiwan Butterfly Conservation Society.

The purple butterfly has purple-brown wings, ringed and covered with white dots. Like the monarch butterfly in Mexico they feed on milkweed, and are also known as milkweed butterflies.

Every year, purple butterflies migrate from the north to the south to spend the cold winter in a valley, and fly back to north Taiwan in late March or early April, covering nearly 400km.

At the height of the migration, along the migration route, one can see up to 10 000 purple butterflies flying overhead.

Taiwan is called the "Kingdom of Butterflies", home to more than 400 species of butterflies. Forty of them can be found only in Taiwan. -- Sapa-dpa



Source (http://www.mg.co.za/articlePage.aspx?articleid=302876&area=/breaking_news/breaking_news__international_news/)