Vol. 28 Núm. 2 (2012)

The life cycle of a desert spider inferred from observed size frequency distribution

Irma Gisela Nieto-Castañeda
Universidad del Mar, Campus Puerto Escondido (UMAR), Ciudad Universitaria, Carretera Vía Sola de Vega, Puerto Escondido, San Pedro Mixtepec, Juquila, Oax., México C.P. 71980 México; Tel: +(52) (954) 954 58 249 90.
saías Hazarmabeth Salgadougarte
Laboratorio de Biometría. Facultad de Estudios Superiores Zaragoza, Universidad Nacional Autónoma de México (FESZ, UNAM), Batalla 5 de mayo S/N esq. Fuerte de Loreto, Ejército de Oriente, Iztapalapa 09230, México, D.F., México.
María Luisa Jiménez-Jiménez
Centro de Investigaciones Biológicas del Noroeste Mar Bermejo 195, Col. Playa Palo de Sta. Rita La Paz, B.C.S., 23090 México Tels: (612) 12 3 8481.

Publicado 2012-08-05

Palabras clave

  • spider life histories,
  • size frequency,
  • kernel density estimators,
  • size classes

Cómo citar

Nieto-Castañeda, I. G., Salgadougarte, saías H., & Jiménez-Jiménez, M. L. (2012). The life cycle of a desert spider inferred from observed size frequency distribution. ACTA ZOOLÓGICA MEXICANA (N.S.), 28(2). https://doi.org/10.21829/azm.2012.282838


We studied the life cycle of the spider Syspira tigrina (Araneae: Miturgidae) by indirect methods. This species is endemic to the North American deserts and locally abundant; nevertheless, information on its biology is scarce. We did monthly collections for over a year at La Paz, Baja California Sur, Mexico. We found that adult spiders were more abundant between August and November 2005 and had low abundance or were absent the remainder of the year while juveniles were present all year. To estimate changing body size structure of the population we analyzed juvenile tibia I length distribution (TIL) (as indicator of the body size) of each monthly sample by means of Kernel Density Estimators (KDEs). We found 35 TIL juveniles size groups (Gaussian components). The smallest juveniles were more abundant between October 2005 and January 2006 and the biggest were more abundant twice during the hottest months. We hypothesize that mating period is between August and October 2005 and the main recruitment period from November 2005 and January 2006. However we found evidence
of continuous recruitment through the year, suggesting that although there is a peak of reproduction in November, the females oviposit almost all year. Also there is evidence of juveniles’ growth pattern from January to July 2006. The use of KDEs with histograms is a very good statistical tool to delimit size groups with mixed frequency distributions that otherwise might be difficult. This tool should be useful to test any hypothesis related with the body size structure of a population or community.