Developing a predictive model of the autecology of the spruce-fir moss spider, Microhexura montivaga crosby and bishop 1925 (araneae: dipluridae).

摘要

The spruce-fir moss spider (Microhexura montivaga) is a federally endangered species of spider found only in the high-elevation Southern Appalachian spruce-fir forests on North-facing slopes underneath moss mats. Despite this fact, little is known about some of the basic ecology of the spider, more specifically the characteristics of the habitat found underneath the moss mats. The goals of this project was to determine the temperature and humidity parameters of the microhabitat conditions around known spider locations, catalogue what other species live there, and use predictive mathematical models created in the Maxent software to estimate past and current locations of potential habitats and identify the key environmental factors that drive such a model. iButton temperature and humidity data loggers placed at Mt. Lyn-Lowry, Browning Knob, Whitetop Mountain and Mt. Rogers (a range that encompasses all metapopulations). Lyn-Lowry and Browning Knob are located in the Plott Balsam range in North Carolina. Whitetop Mountain and Mt. Rogers are located in the Mt. Rogers National Recreation Area in Virginia. No statistically significant differences in daily maximum or minimum temperature between positive and negative presence sites, among metapopulations, or individual sites. A potential set of temperature conversion factors were calculated using percent change for temperature by comparing the collected data, a local weather station, and a U.S. Fish and Wildlife Service deployed HOBO data logger mounted in a tree. Soil samples collected from Blackrock Mountain in the Plott Balsams yielded 2039 individuals comprising 11 orders, with Collembola and Acari being by far the most abundant; this is important as these orders have been hypothesized to be the primary prey items of M. montivaga. Maxent models show the current potential range as well as historical models of the last interglacial period and glacial maximum. Maxent models use presence only data and environmental factors to estimate potential habitat. Range during the last glacial maximum was greater than present range while the range during the last interglacial period was less than present range according to the models. They also include potential range expansion and retraction patterns. All models were heavily driven by temperature environmental layers, in particular those dealing with temperature maximums. This research provides a number of potential applications for the conservation and management of M. montivaga, such as using collected data to determine conversion factors for temperature data between microhabitat measurements and larger scale measuring methods, such as weather stations. For example, HOBO data loggers mounted in trees measure maximum daily temperature higher by 83.5% compared to microhabitat measurements. This allows for large scale monitoring can be done without having to actually measure the temperatures underneath the moss mats. It is hoped that this research, along with the continuing work of U.S. Fish and Wildlife Service, will contribute to a much more positive outlook for this endangered species.