20th International Congress of Arachnology

DENVER MUSEUM OF NATURE & SCIENCE

REPORTS

No. 3, July 2, 2016

Cushing

Student - Oral presentation

Centruroides

as a model to understand

the origin and evolution of venoms

Edmundo González-Santillán, Alfredo Herrera-Estrella

Laboratorio Nacional de Genómica para la Bio-

diversidad, Centro de Investigación y de Estudios

Avanzados del Instituto Politécnico Nacional, Km

9.6 Libramiento Norte Carretera León, C.P. 36821,

Irapuato, Guanajuato, México.

maaykuyak@gmial.com

The genus

Centruroides

is the second most diverse

among North American buthids with Mexican species

representing ca. 40 % of the diversity and 15 medically

important species. The taxonomy of the genus remains

contentious and there is scarce information on its phy-

logeny. Three species groups are recognized in Mexico,

approximately corresponding to three out of four

monophyletic clades recognized by Esposito (2011): 1)

the striped group where all medically and some harm-

less species are grouped, 2) the non-striped group,

and 3) the Thorelli-like group. Important aspects of

Centruroides

toxin biochemistry, pharmacology and

diversity have been discovered in recent years. However,

there has been little attention in integrating this infor-

mation with other disciplines such ecology, population

genetics and epidemiology, especially to investigate the

evolutionary mode and tempo of toxicity in scorpions.

Several competing hypotheses on the origin of toxic-

ity at the molecular level have been proposed but they

have not been validated by other disciplines. The most

appealing hypothesis is that arthropod defensins and

the most potent and lethal gated ionic channel inhibi-

tor toxin family share a common ancestor. We contend

that addressing the origin of toxicity requires simulta-

neous consideration of ecological backdrop, population

genetics, behavior, and prey/predator biology. We are

also convinced that epidemiology could potentially

reciprocally illuminate the evolution of toxicity in

scorpion and scorpionism, a worldwide health problem

recognized by WHO.

Keywords: Scorpiones, toxic peptides, origin and evolu-

tion, multidisciplinary, transcriptome

Student - Poster presentation

Effects of dense taxon sampling, implied

weighting and indels on total evidence

analyses of subfamily Syntropinae (Scor-

piones, Vaejovidae)

Edmundo González-Santillán

, Lorenzo Prendini

Laboratorio Nacional de Genómica para la

Biodiversidad, Centro de Investigación y de Estudios

Avanzados del IPN, Guanajuato, México;

Division of

Invertebrate Zoology, American Museum of Natural

History, New York, USA

maaykuyak@gmail.com

A total evidence phylogeny of the North American vaejovid

scorpion subfamily Syntropinae, based on dense taxon

sampling, is presented. Comprising 462 terminals

and 4273 aligned nucleotides of the mitochondrial 12S,

16S and COI genes and the nuclear 18S and 28S genes, 45

continuous, and 206 discrete morphological characters,

this is the largest matrix ever assembled for scorpions. The

analysis was rooted on

Smeringurus grandis

and other

taxa representing the main clades of the family Vaejovidae.

Using parsimony in the program TNT, the effect of several

parameters on the matrix was compared with a previ-

ously published matrix for the subfamily, comprising 145

terminal taxa. Both matrices were analyzed with equal

weights and implied weights with different values of the

concavity constant (k = 3, 10, 15, 30, 60, 100, 110). The

effect of indels used as missing data or as a fifth state was

also investigated. Tree topologies were compared and sym-

metric resampling and relative Bremer support calculated,

for each analysis. Denser sampling and differing values

of the concavity constant values both influence the topology

and support. The monophyly of taxa was more frequently

recovered and support values slightly greater in the analysis

with denser sampling. More monophyletic groups were

retrieved when indels were analyzed as a fifth state than as

missing data. In summary, adding an approximately four-

fold increase in the density of taxon sampling, resulted in a

more consistent topology, with increased support. The benefit

of analyzing gaps as a fifth state was also demonstrated.

Keywords: Total evidence, Syntropinae, taxon sampling,

implied weights, monophyly, support, indels