Occupancy modelling of nine endemic insects from the Monahans Sandhills in western Texas

A total of nine species of concern in Texas (Anomala suavis, Epitragosoma arenaria, Nicagus occultus, Polyphylla monahansensis, Polyphylla pottsorum, Prionus arenarius, Prionus spinnipenis, Stenopelmatus monahansensis, and Trigonoscutoides texanus) have been the focus of recent surveys initiated in March 2013 at the Monahans sandhills.  In order to provide information that supports threat assessments and conservation actions, it is necessary to determine occupancy patterns for these species.  Seven semi-permanent insect trapping stations were established during March and April 2013 at the Monahans Sandhills State Park on open and vegetated sand dunes.  Data from these stations was analyzed as a single-season occupancy model using the program PRESENCE. Covariates of abundance (number of insects collected) and vegetation (open or vegetated dunes) were included in the analyses. Results indicated that Anomala suavis, Epitragosoma arenaria, Polyphylla monahansensis, Polyphylla pottsorum, Prionus arenarius and Prionus spinnipenis were present at all survey sites, whereas Stenopelmatus monahansensis and Trigonoscutoides texanus where present at only five of the sample locations and with higher abundances on vegetated sites. Nicagus occultus was not found at any of the survey sites, indicating that the trapping methods used for this species where ineffective. In general, models with most support were the less parameterized (assuming one group and constant detection probability among surveys). This study provides an initial occupancy estimate of the Monahans dunes endemic insects; the model provided will be improved by adding more survey sites and museum records.