Report by John T. (Jack) Longino, The Evergreen State College.
The purpose of this report is to give a few statistics on the ant fauna of Costa Rica, Guatemala, and Chiapas, based on all my specimen records. I have not combed the literature for all reports, so there will no doubt be refinement with time.
So far I have recorded 1107 ant species for all three areas combined. 307 of these are morphospecies (most of which are definitely undescribed species), showing that about 70% of the fauna is named. The breakdown by region is Costa Rica 918, Guatemala 408, Chiapas 411. These numbers don't mean much, since the sampling time and effort has been far greater in Costa Rica.
206 species, nearly 20%, are in the hyperdiverse genus Pheidole. No other genus is even close.
A total of 92 genera have been recorded, 87 for Costa Rica, 77 for Guatemala, 78 for Chiapas. Most genera occur throughout the region. The few that are restricted to only the northern or southern portion of the region are discussed below.
Genera with broad ranges in South America, reaching Costa Rica, but not known from Guatemala or Chiapas are Bariamyrma, Basiceros, Carebarella, Centromyrmex, Heteroponera, Lenomyrmex, Paraponera, and Stegomyrmex.
Bothriomyrmex is a largely old-world genus with what appears to be an isolated native species in Costa Rica. These are very small ants easily confused with Tapinoma, so its narrow range could be an artifact of undersampling.
A single worker from Costa Rica is a Hypoponera or Ponera-like ant that may represent an undescribed genus.
Genera that occur in Costa Rica and Guatemala, but not recorded from Chiapas, are Simopelta and Technomyrmex. Simopelta is relatively abundant in the Costa Rican highlands. The type of one species, S. pergandei, is from Guatemala, but Project LLAMA sampling has not yielded any Simopelta from Chiapas or Guatemala. Technomyrmex is mainly old-world. In the Americas there are a few introduced tramp species and a few isolated native species. The native species are allopatric: one in northern Colombia, one in Panama and Costa Rica, and a newly discovered one in Guatemala.
Genera found in Guatemala and/or Chiapas and not in Costa Rica are Cheliomyrmex, Formica, Perissomyrmex, Pogonomyrmex, and Ponera. Formica is a temperate zone lineage reaching its southern limit in the highlands of Chiapas (and Guatemala? I have no records but there may be some). Ponera is mainly old-world, but there is a widespread temperate zone species, P. pennsylvanica, in eastern North America. An allopatric isolate occurs in the highlands of Chiapas and Guatemala, similar to P. pennsylvanica but smaller. Pogonomyrmex is abundant and diverse in arid zones of the southern U.S. and Mexico. A species occurs in arid and dry-forest zones of Guatemala, but then is absent from Honduras to Panama. The genus occurs again in arid zones in Colombia and elsewhere in South America. Cheliomyrmex is a wet forest army ant that occurs in Chiapas and Guatemala, and again in northern South America, but is unknown from in between. Perissomyrmex is a relict lineage with one species endemic to the highlands of Chiapas and Guatemala, and a few other species from the Asian temperate zone.
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.longinoj@evergreen.edu