Geographic Variation in the Mating System of the Mesquite Lizard, Sceloporus grammicus. Sceloporus grammicus. Reproductive Cycles. Reproductive Cycles

Transcription

1 Geographic Variation in the Mating System of the Mesquite Lizard, Sceloporus grammicus Sceloporus grammicus High elevations Viviparous (livebearing) Sites 1983 Reproductive Cycles Reproductive Cycles Many animals not reproductively active at all times of year Many animals not reproductively active at all times of year Usually, cycles synchronous (in phase) between males and females Asynchronous Reproduction Asynchronous Reproduction 1

2 Asynchronous Reproduction In lizards, found in some skinks, at least three species of Sceloporus, and a cordylid Asynchronous Reproduction In lizards, found in some skinks, at least three species of Sceloporus, and a cordylid Requires sperm storage Interpopulation Variation Interpopulation Variation Tamaulipas (low elevation, synchronous male and female cycles) Interpopulation Variation Who stores the sperm? Male lizards may store sperm in epididymides Tamaulipas (low elevation, synchronous male and female cycles) Parque Nacional Zoquiapan (high elevation, asynchronous male and female cycles) 2

3 Who stores the sperm? Male lizards may store sperm in epididymides Female lizards known to have special sperm storage structures Who stores the sperm? Male lizards may store sperm in epididymides Female lizards known to have special sperm storage structures Sperm found in S. grammicus females from asynchronous population at El Capulín, Mexico in September and October Sperm Competition Can occur in any species where multiple males mate with one female Sperm Competition Can occur in any species where multiple males mate with one female Advantage may go to first male, last male, or male who introduces greatest volume of sperm Sperm Competition Can occur in any species where multiple males mate with one female Advantage may go to first male, last male, or male who introduces greatest volume of sperm May be an alternative strategy for males who can t hold territories or monopolize females Alternative Mating Strategies In the side-blotched lizard, throat colors associated with alternative strategies Similar system found in European common lizard, Lacerta vivipara 3

4 QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture. The same three throat colors occur in S. grammicus males as in the sideblotched lizard! The same three throat colors occur in S. grammicus males as in the sideblotched lizard! Tests: intruder trials, lab encounters Tests: intruder trials, lab encounters Field evidence of frequency-dependent selection Monitor populations over several years Skeletochronology Tests: intruder trials, lab encounters Field evidence of frequency-dependent selection Monitor populations over several years Skeletochronology Investigate heritability of throat color and fitness of each strategy with paternity analysis 4

5 Would need to mate guard for longer time period Would need to mate guard for longer time period Sperm mixes in reproductive tract for longer, so opportunity for sperm competition (& cryptic female choice?) greater Would need to mate guard for longer time period 2 primary field sites for population monitoring Sperm mixes in reproductive tract for longer, so opportunity for sperm competition (& cryptic female choice?) greater If strategies associated with throat color, should see differences 2 primary field sites for population monitoring Synchronous: Santiago Tolman 2 primary field sites for population monitoring Synchronous: Santiago Tolman Asynchronous: El Capulín 5

6 Preliminary Results Preliminary Results Blue-throated male lizards at high frequency at Santiago Tolman (synchronous site) Blue-throated male lizards at high frequency at Santiago Tolman (synchronous site) Blue males (mate guarders in U. stansburiana) not present at El Capulín (asynchronous site) Preliminary Results Blue-throated male lizards at high frequency at Santiago Tolman (synchronous site) Blue males (mate guarders in U. stansburiana) not present at El Capulín (asynchronous site) Yay! Future Plans Sample more populations to see if morph differences are consistent Intensive study of El Capulín and Santiago Tolman to determine presence of strategies heritability of throat color whether frequency dependent selection occurs 6