Theses and Dissertations

Date of Award


Document Type


Degree Name

Master of Science (MS)



First Advisor

Dr. Kathryn Perez

Second Advisor

Dr. Andrew McDonald

Third Advisor

Dr. Frank J. Dirrigl Jr.


The lower Rio Grande Valley are three lowest latitudinal counties of south Texas. This unique, subtropical, semi-arid environment has the last remaining Tamaulipan Thornforest in the USA. The Tamaulipan Thornforest of Texas occupies less than 2% of their former range. Before this habitat possibly dwindles even more there has been a comprehensive survey of terrestrial snails in intact, altered, and urban areas of the valley.

We have found a 16397 of snails in intact sites with a high species richness at 17; followed by altered sites with an abundance of 12143 snails and a species richness of 15. There were 7302 snail individuals in urban sites and the lowest species richness out of all three disturbance levels at 10. Paired intact sites compared to their altered sites counterpart were found to have a less diverse snail community, 4.4 mean species richness of intact sites and 9.4 mean species richness of altered sites. This might indicate some snail communities' benefit from disturbance or that the most diverse intact snail communities are so unique they do not have a comparable altered counterpart.

Urban sites, residential yards, were found to have less diversity compared to wild sites, a combination of intact and altered sites; 7.6 mean species richness in urban sites and 4.9 mean species richness in wild sites. This may indicate that urban sites are less beneficial to snail community composition. There are 8 synanthropic and 3 introduced snail species that make up the snail communities of the urban sites. Praticolella mexicana was the most abundant snail found in urban sites. Most snail species found in urban areas are introduced and/or synanthropic, this suggests that urbans sites are safe havens for introduced and/or synanthropic snail species.


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