8/19/2013. What is a community? Topic 21: Communities. What is a community? What are some examples of a herp species assemblage? What is a community?

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1 Topic 2: Communities What is a community? What are some examples? What are some measures of community structure? What forces shape community structure? What is a community? The group of all species living at a and potentially with one another Defined by its features Includes all species, including plants and animals Includes more than can be studied Considers processes and patterns above the What is a community? The species that are studied A subset of a community Often restricted in terms of: of species of species Gives a partial picture of what is going on Our focus here will be community-level processes with herp examples Consider the herps that live in a given locality What are some examples of a herp species assemblage? Area just east of Tucson, Aizona A diverse herp community Species (partial list) Urosaurus ornatus Uta stansburiana Sceloporus clarkii Sceloporus magister Sceloporus undulatus Cophosaurus texanus Phrynosoma solare Aspidoscelis sonorense Elgaria kingi? Crotalus atrox Crotalus molossus Pituophis catenifer Masticophis bilineatus Phrynosomatinae Haekel, Batrachia Photos PJB

2 What are some examples of a herp species assemblage? What are some examples of a herp species assemblage? Yuma, SW Arizona Hotter, drier, lower than Tucson Species (partial list) Sceloporus magister Sceloporus undulatus Callisaurus draconoides Uma notata Phrynosoma mcallii Phrynosoma platyrhinos Dipsosaurus dorsalis Gambelia wislizeni Coleonyx variegatus Crotalus atrox Crotalus cerastes Chionactis occipitalis Masticophis flagellum Phrynosomatinae Photos PJB Osa Peninsula, Costa Rica Squamata Anolis polylepis Anolis capito Basiliscus basiliscus Ctenosaura similis Coniophanes fissidens Ameiva quadrilineata Sphenomorphus cherriei Immantodes inornatus Bothriechis schlageli Anura Leptodactylus pentadactylus Eleutherodactylus spp. Agalychnis callidryas Phrynohyas venulosa Hyla rosenbergi Photos: KP Bergmann; M Fogden; K Warkentin What are some examples of a herp species assemblage? Communities can differ between localities in a region Different species Example below: Local snakes How do we measure community structure? Number of species in a Which species are at a community locality One measure of diversity How do they differ from Also consider morphological, another locality? functional & ecological How closely related to one diversity another are they Valley bottom riparian (mesquite dominant) Mountain canyon riparian (ash dominant) Thamnophis marcianus Thamnophis cyrtopsis Masticophis flagellum Masticophis bilineatus Crotalus scutulatus Crotalus molossus Photos: PJB; W Wells; T Brennan; Lanier et al

3 How do we measure community structure? Relative abundance Also called species evenness Which species are dominant in a community? Which species are rare? Which niches do the different species fill? What are they doing in the community? Haekel, Lacertilia What forces shape community structure?

4 What forces shape community structure? of the species Environmental gradients often determine factors like Latitudinal gradients correlate with both Lower Warmer More humid Greater species richness Other factors, such as biome type also play a role # of Species Anura Gymnophiona # of Species Urodela Testudines Lizards Latitude MI, USA (42) GA, USA (32) Guatemala (6) Costa Rica (0) Ecuador (0) Modified from Pough et al. 2004, Table 6- Climate & physiological tolerance is important Higher elevations are colder Simulate changes in latitude Pough et al. 2004, Fig 5-20, 6- Climate & physiological tolerance Important climatic factors for amphibians and reptiles Amount of Amount of Different clades like different things (Anura vs. Squamata) This will influence Species richness Species evenness Species composition Correlations with species richness US & Australia Taxon Anura Testudines Lizards Hours Sun Precip Temp What kinds of interspecific interactions are there? How would you expect each one to influence a species or a community? (Species richness, occurrence, abundance, niche) Modified from Pough et al. 2004, Table 6-2 Pough et al. 2004, Fig 6-0

5 Some species are better competitors than others Thai tadpole assemblage Different species inhabit different parts of water column Forage for different things Can coexist Also temporal partitioning: some species hatch earlier than others Interspecific interactions complexity Anolis lizards partition their habitat in various ways occurs on the tiny Lesser Antilles Some islands have species Intermediate body size Larger islands have 2 species One species is small One species is large The species fill different niches There are strong phylogenetic effects Pough et al. 2004, Fig 6-0 Butler and Losos 997 Interspecific interactions Anolis habitat use changes with increased changes with number of species Anolis sagrei Perch diversity decreases with increasing number of sympatric species Males Females can influence Changes selective pressures Anolis sagrei on islands with Leiocephalus carinatus L. c. is a terrestrial predator Influences habitat use and selection Photo I Sevi Pough et al. 2004, Fig 6-6 Losos et al Can decrease interspecific Can lead to some species thriving Newt (Notophthalmus) is a predator of various frog tadpoles When predation is high, the Pseudacris crucifer tadpoles are significantly larger Less competition for food with other species May also be more resistant to predation Continuing with Pseudacris example When newts are absent, Pseudacris is outcompeted by other species When newts are in high density, Pseudacris dominate the assemblage Pough et al. 2004, Fig 6-3 Pough et al. 2004, Fig 6-2

6 History Anthropogenic Effects Our activities Is a clade species rich or not? Closely related species often are more similar ecologically May not live in the same community due to competition Are species from a clade present in the area? How many species from the clade? Which clade got there first? Some species do well in anthropogenic ecosystems, others do not Urban Arizona Species Rural Arizona Species Hemidactylus turcicus NOT Hemidactylus turcicus Callisaurus draconoides Also Holbrookia maculata Sceloporus undulatus Sceloporus clarkii Urosaurus ornatus Masticophis spp. Sceloporus magister Other Crotalus Aspidoscelis sp. Gopherus agassizii Crotalus atrox Etc. Noonan & Chippindale 2006; Duellman & Pianka, 990 Photo S Renzl Anthropogenic Effects Introduced species act as and to native species Mongoose, goats, cats, rats, cane toad, etc. Islands are highly affected/vulnerable Bufo marinus Introduced to E Australia ~940 Biological control of Cane Beetle Spread rapidly Anthropogenic Effects Impacts of Bufo marinus Competitor Predator Poisons native predators Incl. Crocodylus johnstoni High native anuran tadpole mortality with Bufo marinus eggs and tadpoles Photos: wikipedia; Australian Gov t Photo: M Letnic; Fig: Crossland