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Other University Microfilms International DIPLOPODA OF A MICHIGAN BEECH-MAPLE FOREST POPULATION ECOLOGY AND SEASONAL ACTIVITY by Vivian Mestey-Villarail A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Zoology ABSTRACT DIPLOPODA OF A BEECH-MAPLE FOREST: POPULATION ECOLOGY AND SEASONAL ACTIVITY By Vivian Mestey-Villamil The present study assessed some aspects of population density, vertical and horizontal distribution, and activity of the dominant diplopod species of Baker woodlot, a beech-maple forest, in Michigan. Field work was focused on quantitative sampling of leaf litter, organic layer and A horizon. Pitfall traps were used to assess seasonal activity during two consecutive years (1984-1985). Of six diplopod species collected in the study area only three were common enough for quantitative analysis: Ophylulus pilosus (Newport), Polydesmus lnconstans Latzel, and Polyzonium blvirgatum (Wood). Ophylulus pilosus was the dominant species. Vertical migration and distribution of the life stages of 0. pilosus was affected by climatic parameters such as seasonal temperature and precipitation. Differences in these two parameters among years also affected population density of the species. Ophylulus pilosus can overwinter in any stage (small juvenile, juvenile or adult), except probably as eggs, which are laid during spring and summer. Adults were common in spring and were present in every s o i l la y e r. Inm ature sta g e s were most common, during summer and fall, in 0 and A horizons. The horizontal distribution of the dominant species could not be related to the amount of litter or its moisture content. Data from pitfall traps showed different activity peaks for each species. Ophylulus pilosus was mainly active in spring, P. lnconstans during summer and P. bivirgatum In the fall. Adults were the most active stage in every species, and both sexes were equally active, indicating that activity peaks of each species corresponded to their matting season. To my husband, family and friends ii ACKNOWLEDGEMENTS I wish to thank the members of my guidance committee: Dr. Richard Snider, Dr. Max Hensley, and Dr. Donald Straney, Department of Zoology, and Dr. Peter Murphy, Department of Botany and Plant Pathology for their assistance in the course of this study. To my major professor, Dr. Renate Snider, I express sincere appreciation for helping me during the preparation of this dissertation. I also wish to thank the University of Puerto Rico for their financial support throughout these years. Very special thanks to my family, friends and my husband, Waldo, for their patience, love and understanding. iii TABLE OF CONTENTS Page List of Tables ................................................................................................................. v l List of Figures ........................................... ................................... v i i PART I - INTRODUCTION .......................................................................................... 1 PART I I - MATERIALS AND METHODS .................................................................... 7 1. Description of the study area ........................................................ 7 2. Sampling methods......................................................................................... 7 2.1. Quadrat sampling ....................................................................... 8 2.2. Pit-trapping ................................................................................ 10 2.3. Classification of life stages ...................................... 14 2.4. Soil moisture determination ............................................ 15 2.5. Litter mass determination ................................................ 15 2.6. Temperature and precipitation ....................................... 15 PART I I I - RESULTS AND DISCUSSION .................................................................. 16 1. Physical parameters ................................................................... 16 1.1. Daily temperatures .................................................................. 16 1.2. Daily precipitation ............................................................... 16 1.3. Substrate moisture .................................................................. 21 A) Leaf litter ........................................................................ 21 B) 0 l a y e r ................... 23 C) A la y e r .................................................................................... 23 1.4. Litter cover ............................................................................ 23 2. Species dominance ..................................................................................... 25 3. Population density .................................................................................. 29 4. Population stage structure ............................................................... 32 5. Spatial distribution of the dominant species ................... 36 5.1. Seasonal horizontal dispersion .................................... 36 5.2 Horizontal distribution and litter mass ................ 38 iv 6. Vertical distribution of the dominant species ............... 46 6.1. Seasonal distribution ......................................................... 46 6*2. Stage-specific distribution .......................................... 46 A.l) Small juveniles ............................................... 46 A.2) Juveniles .............................................................. 54 A.3) Adults ..................................................................... 56 7. Surface activity ....................................................................... 57 7.1. Total number of individuals captured .................... 57 7.2. Stage-specific activity .................................................... 59 7.3. Seasonal activity patterns ............................................. 61 A) At sp e c ie s le v e l .............................................................. 61 B) At sta g e le v e l ................................................................... 68 C) Sex-related differences in adult stage .... 70 C.l) Ophylulus pilosus .......................................... 75 C.2) Polydesmus lnconstans ................................ 76 C.3) Polyzonium bivirgatum ..................... 76 PART IV - SUMMARY AND CONCLUSIONS .............................................................. 78 BIBLIOGRAPHY ......................................................................................... 82 v LIST OF TABLES Table Page 1. Inter-trap distances ....................................... 12 2. Characteristics o£ developmental stages used to classify Ophyiulus pilosus .................................................................. 13 3. Characteristics of developmental stages used to establish categories for Polydesmus lnconstans .................. 14 4. Average dry mass of