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Wheeler, Gregory [1], Mcglaughlin, Mitchell [2], Helenurm, Kaius [3], Wallace, Lisa [4].

Importance of Inter-island Dispersal in Explaining Genetic Structure in Acmispon argophyllus (Fabaceae) on the California Channel Islands.

The California Channel Islands are known for high levels of endemic floral diversity. The current geological understanding of this system indicates that none of the eight Channel Islands have ever been connected to the California mainland, and the four southern islands have remained separated even during the last glacial maximum. Given this, over-ocean dispersal is required to explain the presence of conspecific populations on multiple islands. One particular possibility that merits examination is the movement of fruits, seeds, and plant material carried by the currents of the Southern California Bight. Two routes of water movement, a current and a counter-current, are known for this region. We examined the potential for these currents to explain the distribution of Acmispon argophyllus on the four southern islands: Santa Barbara, Santa Catalina, San Clemente, and San Nicolas. We hypothesized that populations with shared ocean current pathways would exhibit greater genetic similarity than populations not sharing ocean currents. Specifically, we hypothesized that populations on Santa Catalina Island serve as a source of colonists to Santa Barbara Island and later, either directly or by island-hopping, to San Nicolas Island. We also hypothesized three possibilities for populations on San Clemente: 1) from Santa Catalina Island, 2) from San Nicolas Island, or 3) from mainland California. Multilocus chloroplast sequences were collected from 144 individuals across 12 populations on the four islands. Pairwise FST analysis revealed similarities between populations on northern Santa Catalina and Santa Barbara Island and San Nicolas Island, with values suggesting separate colonizations of the latter two islands from Santa Catalina. These data also suggested at least two independent origins of populations on San Clemente Island, with one lineage likely derived from populations on Santa Catalina. These findings are supported by the structure of a haplotype network, which showed two major clusters, one of which is dominated by haplotypes derived from those found on Santa Catalina and the other containing independently derived haplotypes. These results add to understanding phylogeographic patterns throughout this island system and demonstrate the importance of considering complex dispersal patterns when investigating the origins of endemic taxa on the Channel Islands.

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1 - Mississippi State University, Biological Sciences, PO Box GY, Mississippi State, MS, 39762, USA
2 - University Of Northern Colorado, 501 20th St, Box 92, Greeley, CO, 80639, USA
3 - University Of South Dakota, Department Of Biology, Vermillion, SD, 57069, USA
4 - Mississippi State University, PO Box GY, Mississippi State, MS, 39762, USA

Channel Islands.

Presentation Type: Oral Paper:Papers for Topics
Session: 2
Location: Franklin B/Hyatt
Date: Monday, July 9th, 2012
Time: 11:00 AM
Number: 2010
Abstract ID:839

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