Biodiversity in assisted migration trials : a study comparing the arthropod diversity between different populations of cottonwood (Populus Fremontii) translocated to new areas

University essay from SLU/Dept. of Wildlife, Fish and Environmental Studies

Abstract: This study aims at investigating how diversity and community structure of arthropods are affected by assisted migration of foundation species. This is proposed to counter biodiversity loss in the tracks of climate change. By focusing on foundation species, a larger quantity of biodiversity could be protected. I investigated arthropod diversity and community structure linked to nine Freemont cottonwood (Populus fremontii) populations types from different areas planted in three common gardens at different elevations. In accordance with the mid-elevation hypothesis that states that diversity peaks at mid-elevations, the diversity and most abundances of arthropod peaked in a mid-elevation garden at 1000 m.a.s.l. However, abundances of the functional group of predators peaked at low elevations contradicting the mid-elevation diversity pattern. Earlier studies have found that genetics and local adaptation exists between arthropods and host plants. Therefore, it was hypothesized that arthropod diversity would differ between cottonwood populations with different origin. The results were non-significant but there were signs of some cottonwood populations holding a higher diversity of arthropods. The result was inconclusive although there were signs of some populations supporting higher diversities than the rest. There was an interaction effect between common gardens and cottonwood population where the most abundant population types contained higher abundances of arthropods in mid-elevation garden. The analysis were performed with a GLM (Generalized linear model) and a Tukey HSD (honest significant difference) and the variables tested was SWD Index (Shannon-Winer diversity index), Evenness and abundances. The results from this study implement that the success of assisted migration and interaction with diversity linked to foundation species need to be further investigated. The findings in this study could be the result of a variety of underlying processes, from species interactions and genetic adaptation in the foundation species and arthropod communities. Both genetics in the plants as well as the arthropod abundances linked to these trees are baselines for the rest of the biodiversity. Both biotic and abiotic factors are important for the success of assisted migration of foundation species as a counter measure to biodiversity loss.

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