What causes speciation?

2019 ◽  
pp. 83-109
Author(s):  
Timothy G. Barraclough
Keyword(s):  
New Species ◽  
Divergent Selection ◽  
Genetic Response ◽  
Geographical Isolation ◽  
Integrated Theory

The balance of evidence from earlier chapters is largely consistent with the reality of species units. This chapter therefore moves on to investigate what causes new species to form. This process involves a series of steps involving the origin of new diversifying conditions, the genetic response of the organisms to those conditions, the persistence of the newly diverged species, and the re-establishment of diversifying conditions in one or more of the descendants to restart the process. Distinguishing the role of geographical isolation and divergent selection in this process, the chapter reviews the theory and evidence for the causes of speciation from systematic evidence across whole clades. In particular, it focuses on whether speciation depends more on the extrinsic conditions favouring divergence or the intrinsic responses of the affected organisms. More integrated theory and coordinated efforts to uncover speciation dynamics for whole clades or regions are needed to answer these questions.

Review of the genus Cnemaspis Strauch, 1887 (Sauria: Gekkonidae) in Sri Lanka with the description of five new species

Zootaxa ◽  
2007 ◽  
Vol 1490 (1) ◽  
pp. 1-63 ◽  
Author(s):  
L. J.MENDIS WICKRAMASINGHE ◽  
D. A.I. MUNINDRADASA
Keyword(s):  
New Species ◽  
Sri Lanka ◽  
Morphometric Analysis ◽  
Mountain Region ◽  
Geographical Isolation ◽  
Morphological Comparison ◽  
Type Series ◽  
Dry Zone ◽  
High Degree ◽  
Wet Zone

Five new species of geckos are described from Sri Lanka by morphological comparison and morphometric analysis leading to review the genus Cnemaspis in the country. The type series of these species were identified from following localities: C. alwisi and C. kumarasinghei from the intermediate zone, C. retigalensis from the dry zone, C. molligodai from the lowland wet zone and C. samanalensis from the mountain region of the wet zone in the country. The high degree of endemicity (90%) shown by Cnemaspis in Sri Lanka could be attributed to geographical isolation. In addition, the taxonomic issue of C. jerdonii scalpensis is discussed and the species C. scalpensis is errected.

scholarly journals On the Critical Role of Divergent Selection in Evolvability

2016 ◽  
Vol 3 ◽  
Author(s):  
Joel Lehman ◽  
Bryan Wilder ◽  
Kenneth O. Stanley
Keyword(s):  
Critical Role ◽  
Divergent Selection

scholarly journals Geographical and social isolation drive the evolution of Austronesian languages

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0243171
Author(s):  
Cecilia Padilla-Iglesias ◽  
Erik Gjesfjeld ◽  
Lucio Vinicius
Keyword(s):  
Social Structure ◽  
Population Size ◽  
Social Isolation ◽  
Linguistic Diversity ◽  
Cultural Group ◽  
Geographical Isolation ◽  
Austronesian Languages ◽  
New Words ◽  
Gain Loss

The origins of linguistic diversity remain controversial. Studies disagree on whether group features such as population size or social structure accelerate or decelerate linguistic differentiation. While some analyses of between-group factors highlight the role of geographical isolation and reduced linguistic exchange in differentiation, others suggest that linguistic divergence is driven primarily by warfare among neighbouring groups and the use of language as marker of group identity. Here we provide the first integrated test of the effects of five historical sociodemographic and geographic variables on three measures of linguistic diversification among 50 Austronesian languages: rates of word gain, loss and overall lexical turnover. We control for their shared evolutionary histories through a time-calibrated phylogenetic sister-pairs approach. Results show that languages spoken in larger communities create new words at a faster pace. Within-group conflict promotes linguistic differentiation by increasing word loss, while warfare hinders linguistic differentiation by decreasing both rates of word gain and loss. Finally, we show that geographical isolation is a strong driver of lexical evolution mainly due to a considerable drift-driven acceleration in rates of word loss. We conclude that the motor of extreme linguistic diversity in Austronesia may have been the dispersal of populations across relatively isolated islands, favouring strong cultural ties amongst societies instead of warfare and cultural group marking.

scholarly journals Understanding the evolution of phenotypical characters in the Micarea prasina group (Pilocarpaceae) and descriptions of six new species within the group

MycoKeys ◽  
2019 ◽  
Vol 57 ◽  
pp. 1-30
Author(s):  
Beata Guzow-Krzemińska ◽  
Emmanuël Sérusiaux ◽  
Pieter P. G. van den Boom ◽  
A. Maarten Brand ◽  
Annina Launis ◽  
...  
Keyword(s):  
New Species ◽  
Secondary Metabolites ◽  
Phylogenetic Analyses ◽  
Morphological Characters ◽  
Its Rdna ◽  
Ancestral State ◽  
Secondary Substances ◽  
Gyrophoric Acid

Six new Micarea species are described from Europe. Phylogenetic analyses, based on three loci, i.e. mtSSU rDNA, Mcm7 and ITS rDNA and ancestral state reconstructions, were used to evaluate infra-group divisions and the role of secondary metabolites and selected morphological characters on the taxonomy in the M.prasina group. Two main lineages were found within the group. The Micareamicrococca clade consists of twelve species, including the long-known M.micrococca and the newly described M.microsorediata, M.nigra and M.pauli. Within this clade, most species produce methoxymicareic acid, with the exceptions of M.levicula and M.viridileprosa producing gyrophoric acid. The M.prasina clade includes the newly described M.azorica closely related to M.prasina s.str., M.aeruginoprasina sp. nov. and M.isidioprasina sp. nov. The species within this clade are characterised by the production of micareic acid, with the exception of M.herbarum which lacks any detectable substances and M.subviridescens that produces prasinic acid. Based on our reconstructions, it was concluded that the ancestor of the M.prasina group probably had a thallus consisting of goniocysts, which were lost several times during evolution, while isidia and soredia evolved independently at multiple times. Our research supported the view that the ancestor of M.prasina group did not produce any secondary substances, but they were gained independently in different lineages, such as methoxymicareic acid which is restricted to M.micrococca and allied species or micareic acid present in the M.prasina clade.

Five new thelotremoid Graphidaceae from the Philippines

Phytotaxa ◽  
2014 ◽  
Vol 189 (1) ◽  
pp. 282 ◽  
Author(s):  
EIMY RIVAS PLATA ◽  
HARRIE J. M. SIPMAN ◽  
ROBERT LÜCKING
Keyword(s):  
New Species ◽  
Rain Forest ◽  
The Philippines ◽  
New Combination ◽  
Historical Collections ◽  
Biotic Diversity

Five new species of thelotremoid Graphidaceae are described from the Philippines: Myriotrema subviride Rivas Plata, Sipman & Lücking, differing from Myriotrema viride in the more prominent ascomata and transversely septate ascospores; Ocellularia gigantospora Rivas Plata, Sipman & Lücking, differing from O. ripleyi in the uncarbonized, ecolumellate ascomata and the larger ascospores; O. leucocavata Rivas Plata, Sipman & Lücking, differing from O. cavata in the uncarbonized ascomata and the larger ascospores; O. sublaeviusculoides Rivas Plata, Sipman & Lücking, differing from O. laeviusculoides in the erumpent ascomata with black columella; and Thelotrema philippinum Rivas Plata, Sipman & Lücking, differing from Thelotrema suecicum in the stictic acid chemistry. The new combination Ocellularia megalospora (Müll. Arg.) Lücking is also proposed. Three of the new species are based on historical collections from vanished rain forest areas on the island of Luzon and are probably extinct, emphasizing the role of herbaria in documenting biotic diversity from threatened ecosystems.

Human Taxonomies: Carl Linnaeus, Swedish Travel in Asia and the Classification of Man

Itinerario ◽  
2019 ◽  
Vol 43 (02) ◽  
pp. 218-242
Author(s):  
Christina Skott
Keyword(s):  
Eighteenth Century ◽  
New Species ◽  
Southeast Asia ◽  
Travel Literature ◽  
Homo Sapiens ◽  
East India Company ◽  
Carl Linnaeus ◽  
Eyewitness Reports

AbstractThis article looks at ways in which Swedish travel to Asia informed the classification of man in the work of Carl Linnaeus. In the tenth edition of his Systema Naturae (1758), Linnaeus made substantial changes to his earlier taxonomy of humans. Through two case studies, it is argued that these changes to a great extent were prompted by fresh Swedish eyewitness reports from China and Southeast Asia. The informants for the Homo asiaticus, a variety of Homo sapiens, and a proposed new species of humans, Homo nocturnus (or troglodytes), were all associated with the Swedish East India Company. The botanical contribution by men trained in the Linnaean method travelling on the company's ships has long been acknowledged. In contrast to the systematic collecting of botanical material, Swedish descriptions of Asia's human inhabitants were often inconclusive, reflecting the circumstances of the trade encounter. Linnaeus also relied on older observations made by countrymen, and his human taxonomies also highlight the role of travel literature in eighteenth-century anthropology.

A new species of Lerista Bell, 1833 (Reptilia: Scincidae) from Cape York Peninsula, Queensland, belonging to the Lerista allanae clade but strongly disjunct from other members of the clade

Zootaxa ◽  
2019 ◽  
Vol 4613 (1) ◽  
pp. 161-171
Author(s):  
ANDREW P. AMEY ◽  
PATRICK J. COUPER ◽  
JESSICA WORTHINGTON WILMER
Keyword(s):  
New Species ◽  
Sea Level ◽  
Suitable Habitat ◽  
Sea Level Changes ◽  
Cape York ◽  
A New Species

A species of the skink genus Lerista is described from Cape York Peninsula in Queensland.  The species is biogeographically interesting as it appears to be separated by at least 500 km from its nearest relatives, members of the Lerista allanae clade.  The role of Pleistocene sea level changes altering availability of suitable habitat for these sand specialists is discussed as a possible driver of isolation and speciation. 

First records of Net-winged Midges (Diptera: Blephariceridae) from Papua New Guinea, with description of a new species

1989 ◽  
Vol 40 (4) ◽  
pp. 361 ◽  
Author(s):  
P Zwick ◽  
KG Hortle
Keyword(s):  
New Species ◽  
Papua New Guinea ◽  
New Genus ◽  
New Guinea ◽  
First Report ◽  
The Family ◽  
Fly River ◽  
A New Species

Curupirina papuana sp. n. and an unnamed species of a probably new genus of Apistomyiini (Diptera : Blephariceridae) are described from the Ok Tedi, a tributary of the Fly River, Papua New Guinea. This is the first report of the family from the island; its zoogeographical significance is discussed with reference to the long-presumed role of the island in the evolution and dispersal of the tribe Apistomyiini.

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