Species complex, cryptic species and the need for Integrative taxonomy

Transcription

1 Species complex, cryptic species and the need for Integrative taxonomy K. Praveen Karanth CES, IISc, Bangalore National Seminar on Conservation Biotechnology and DNA Barcoding, th May 2015 Gujarat Biodiversity Gene Bank

2 Phylogeny of langurs of the Indian subcontinent Purple-faced Hanuman SL Hanuman Sl Nilgiri Hanuman N Hanuman N 4 Silvered Dusky Phayre's (I) Phayre's (V) Francois' Karanth et al. (2005) Molecular Phylogenetics and Evolution

3 Spalax galili, 2n=52 is distributed predominantly in the cool and humid Upper Galilee Mountains In Israel the 4 chromosomal (cryptic) species are distributed parapatrically in 4 climatic regimes Spalax golani, 2n=54 is distributed in the cool and semi-dry Golan Heights Spalax carmeli, 2n=58 is distributed in the humid and warm Lower Galilee Mountains and central Coastal Plains Spalax judaei, 2n=60 is distributed in the warm and dry southern Coastal Plains and northern Negev Desert Karanth et al. 2004

4 Both Hanuman langur and blind mole rat are widely distributed. Widely distributed species are often species complexes and harbor cryptic diversity. Species complex: Group of closely related, morphologically similar species that have been assigned to a single species. Cryptic species: two or more species that are morphologically identical/similar.

5 Spatial heterogeneity in climate and topography Additional layers: Soil and temperature map Images by Deepak V.

6 Issue with species complex Much of species identification and description based on morphology. This is a problem because one cannot distinguish cryptic species morphologically. How do we delimit (cryptic) species? What is a species? Ernst Mayr(1942) species problem Over 20 species concepts

7 Species concepts Morphological (or Phenetic) Species Concept (MSC) Morphospecies -Members of a species are morphologically similar to each other, Fixed character difference (taxonomists). Biological Species Concept (BSC) -Individual that are interfertilebelong to the same species Ecological Species concept Set of organisms exploiting a single niche (adaptive zone) Phylogeny-based concepts -Evolutionary species concept (ESC) A lineage evolving independently -Phylogenetic species concept (PSC) Smallest diagnosable monophyletic group -genealogical species concept (GSC) Mutually monophyletic in the genealogies of all genes Lineage species concept (LSC)=General concept of species (GCS)

8 de Queiroz(1998, 2007), noted that the various species concepts (such as BSC, PSC, ESC etc) are related to diversity of events or subprocessesthat occur during speciation and that all modern species definitions are variations of the same general species concept which he calls the lineage species concept or general concept species. Species are segments of separately evolving metapopulation lineages. Lineage refers to an ancestor-descendant series, in this case of metapopulationsor simply a metapopulationextended through time. Metapopulationrefers to an inclusive population made up of connected subpopulations.

9 Thus, under all species concepts, a species is a separately evolving metapopulationlineage, but under the isolation version of the biological species concept, the lineage also has to be intrinsically reproductively isolated from other lineages; under the ecological species concept, the lineage also has to occupy a different niche; under the phenetic species concept, it also has to be phenetically distinguishable; under the phylogenetic species concept (monophylyversion), it also has to be monophyletic in terms of its component genes, organisms, or subpopulations, and so forth. The diversity of events or subprocesses that occur during speciation do not always occur in the same order.

10 How do we delimit species? Presence of any one of the properties (subprocesses) is evidence for the existence of a species, though more properties and thus more lines of evidence are associated with a higher degree of corroboration (de Queiroz, 2007). The actual demarcation of species taxauses morphological, geographical, ecological, behavioral, and molecular information to infer the rank of isolated populations (Ernst Mayr, 1996) Multiple lines of evidence, multi-dimensional approach Integrative taxonomy! MD RI ED 1) Morphological divergence MD(MSC) 2) Ecological divergence ED (Ecological SC) 3) Reproductive isolation RI(BSC) 4) Reciprocal monophyly RM(PSC) 5) Behavioral divergence BD(such as call, RSC) MD RI BD RM Good species BD RM ED

11 Lineage species concept/ Integrative taxonomy and Indian systems

12 S. entellus Semnopithecus complex S. hypoleucos Mitochondrial Cytochrome b tree NJ/MP/Bayesian approaches S. priam+ S. johnii

13 S. entellus S. hypoleucos Nuclear NJ tree based on four markers S. priam S. johnii AshalakshmiC.N

14 Hemidactylus brookii complex Aparna Lajmi

15 Sitana ponticeriana complex Deepak V.

16 Late Cretaceous diversification among peninsular Indian centipedes suggest their Gondwanan origin Cormocephalus Scolopendra Digitipes COI, 12S rrna 28S rrna Likelihood tree Ethmostigmus Rhysida 200 Jurassic 150 Cretaceous 100 Tertiary 50 MYA Jahnavi Joshi

17 Digitipes species complex mtdna tree Nuclear DNA tree Separation on Env. axis (PCA) Morphology tree Traditional Taxonomy Species 1 χ χ# D. coonoorensis Group A Species 2 χ χ+ D. indicus Species 3 χ cf D. barnabasi Group B Group C Species 5 Species 7 χ χ# cf D. coonoorensis cf D. barnabasi Species 6 Species 8 χ χ# cf D. coonoorensis D. barnabasi Group D Species 9 NA χ+ D. sp

18 How to detect and delimit cryptic species 1a 1b 1a 1b Species 1 consists of 2 species (a,b)? Intraspecific population structure? 2 2 Cryptic species 3 3 Use speciation models to detect putative species Rosenberg s P, PTP, Bayesian approach Integrative taxonomy, multiple lines of evidence

19 Species complexes from the Indian subcontinent TT IT Reference Primates Semnopitheus 3 6 Ashalakshmi et al. (2015) Reptiles Sitana 1 >18 Deepak et al. (in prep.) Geckoella 7 14* Agarwal& Karanth(2015) H. brookii 1 5 Lajmi et al. (submitted) C. aravallense 1 7* Agarwal et al. (2014a) Cyrtodactylus(I) 5 22* Agarwal et al. (2014b) Amphibians Raorchestes 43 52(9) Vijayakumar et al. (2014) Invertebrates Digitepes 3 6 Joshi & Karanth(2012) Itaropsis 1 >3 Jaiswaraet al. (2012). TT: Traditional taxonomy IT: Integrative taxonomy *Molecular data suggests multiple species

20 Implications Widely distributed species might be a species complex Cautionary note: interspecific rather than Intraspecific comparison, example Hanuman langur Application of new methods for diagnosing species Morphology as the sole criteria for species description obsolete Acoustic, behavioural, anatomical, skeletal, chromosomal, olfactory cues (chemical) and molecular data Newton 1988 Diversity under estimated Next frontier in biodiversity research in the tropics? What groups to target? Invertebrates (need not be widely distributed), small widely distributed vertebrates Dispersal ability might be important