A model of the longterm persistence of the valley elderberry longhorn beetle

Graduation Date

2010

Document Type

Thesis

Program

Other

Program

Thesis (M.S.)--Humboldt State University, Environmental Systems: Mathematical Modeling, 2009

Committee Chair Name

Borbala Mazzag

Committee Chair Affiliation

HSU Faculty or Staff

Keywords

Humboldt State University -- Theses -- Mathematical Modeling, Metapopulation, Valley elderberry longhorn beetle

Abstract

The valley elderberry longhorn beetle (VELB) lives in elderberry bushes in the Central Valley of California. It is threatened under the Endangered Species Act and is also of theoretical interest because it persists at low densities in a patchy landscape. It is thought to exhibit many of the characteristics of a classical metapopulation. The life cycle of VELB consists of eggs, larvae and adults. Beetles are eggs for a few days, larvae for one or two years, and adults for a few weeks. The larvae live inside and eat the pith of elderberry stems (Talley, 2005). Since, VELB exist in small local populations, we propose stochastic migration and reproduction could be important to the long term persistence of the VELB. We study how habitat configuration, dispersal range and density dependence may effect the persistence of the VELB. We develop a stochastic two age structured model; the Adults can migrate, and the Juveniles cannot. There is density dependence on the eggs and early larval stage. In our model, beetles tend to stay on the bush they were born on. We run simulations to study the effects of differing types of density dependence, differing variations of our migration rule, and different habitat configurations. We found that having a lot of patches allows beetles to persist in a landscape over many years. We also found that not all bushes must be occupied for the the population to persist. The implications of our results for conservation are consistent with existing management plans.

https://scholarworks.calstate.edu/concern/theses/dn39x387d

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