30 captures

12 Feb 2001 - 28 Jun 2023

Sep MAR May 11

2004 2007 2008

success

fail

About this capture

COLLECTED BY

Organization: Alexa Crawls

Starting in 1996, Alexa Internet has been donating their crawl data to the Internet Archive. Flowing in every day, these data are added to the Wayback Machine after an embargo period.

Collection: 38_crawl

this data is currently not publicly accessible.

TIMESTAMPS

The Wayback Machine - https://web.archive.org/web/20070311042359/http://darwin.eeb.uconn.edu:80/eeb310/lecture-notes/checkerspot/node4.html

Local Extinction

In 1997 the Jasper Ridge population of the bay checkerspot declined to extinction [1]. The discovery of the large population near Morgan Hill in the mid-1980's made Ehrlich, Murphy, and colleagues believe that they could learn more from watching the Jasper Ridge population decline to extinction than by intervening to prevent its extinction.

In a similar vein, populations of a different subspecies of Euphydryas editha underwent a drastic change in the central Sierra Nevada [4]. Clearcutting of the forest in part of Sequoia National Forest in 1967 created artificial meadows that were excellent habitat, and the butterflies switched to a different food plant that was very abundant there, Collinsia torreyi.

• Populations in clear-cut areas behaved as source populations.
  • They produced an excess of offspring every year, and some of that excess resulted in migrants to nearby native populations on rock outcrops.

  • Population sizes on outcrops were larger the closer those populations were to clearcut populations.

  • Individual breeding success was poor in outcrop populations.

• During a severe drought in 1992, plants of C. torreyi did not survive, but the host plants used by checkerspots in outcrop populations persisted.

• Clear-cut populations of checkerspot declined to extinction, while outcrop populations persisted.