Urban Ant Fauna of Port of Spain, Trinidad, West Indies

Christopher K. Starr1 and Shane T. Ballah2

  1. Caura Village, Trinidad and Tobago
  2. STB Consulting, 19 Stanmore Avenue, Port of Spain, Trinidad and Tobago

Corresponding author: ckstarr@gmail.com

ABSTRACT

A one-day survey of ants in the city of Port of Spain yielded 154 samples representing 23 species. The greater part of these were found in two relatively well-vegetated areas. The pattern of samples gives a diversity index of H’ = 2.39 and an estimate of the number of species present but not collected of f0 = 5.3. The overall faunal composition was largely as expected, with no notable distinction between daytime and nighttime sampling except for the strictly nocturnal presence of Camponotus atriceps.

 

Key words: neotropical, diversity

INTRODUCTION

Habitat disturbance is well known to diminish species diversity, and urbanisation is the most severe of all very widespread forms of terrestrial disturbance. Ants (Hymenoptera: Formicidae) are a prominent feature in virtually all terrestrial habitats. With about 16,000 known species (Bolton et al. 2007) and an enormous density of individuals, they are a key ecological force (Hölldobler and Wilson 1990). 209 species are recorded from Trinidad, West Indies (Starr and Hook 2003), although the true total is certainly substantially higher. Although urban environments are certainly relatively poor in species of ants, no unitary trend has yet appeared in this trend (Philpott et al. 2010). Our purpose here is to report a preliminary survey of ants in a tropical city, with comments on the findings.

 

MATERIALS AND METHODS

All collecting was on 5 November 2016 in the city of Port of Spain, Trinidad & Tobago. Our focus was entirely urban and external, extending from the north end of the Queen’s Park Savanna to the area in and around the Lapeyrouse Cemetery (10°40’N 61°31’W), disregarding the nearby Royal Botanic Garden and other garden-like localities. We collected about two-thirds of our samples in the morning between 08:00-12:00h, the rest in the early night between 18:30-20:00h.

Ants, like other social insects, occur in more or less discrete groups (colonies). Accordingly, our sampling and analysis were based on colonies, rather than individual organisms. We walked slowly while scanning the ground and tree trunks. On encountering ants, we collected one or a few apparent nestmates, after which we walked an estimated five meters further before resuming the search. This five-meter interval was to minimize the likelihood of taking to samples from a single colony.

We later sorted all samples into morphospecies, which we identified to genus and in a few cases to species by reference to Hölldobler and Wilson (1990) and other identification materials. Specimens are deposited in the University of the West Indies Zoology Museum Land Arthropod Collection (UWIZM).

 

RESULTS AND DISCUSSION

Our 154 samples represent 23 morphospecies (Table 1). The faunal composition contained no surprises, except perhaps for the paucity of Pheidole. Our comparison between the day and night fauna was far from rigorous. Nonetheless, it allows the rough generalisation that these are much the same except for the nocturnal habit of Camponotus atriceps.

Although there is no known way to predict the ant fauna of a disturbed habitat, the species richness in our samples was greater than expected. The Shannon diversity index (Magurran 2004) yields a moderately high figure of H’ = 2.39. Eight of our morphospecies were represented by a single sample (singletons) and another six by two samples (doubletons). Applying the Chao1 method (Gotelli and Colwell 2011) estimates the number of undiscovered species at f0 = 5.3. That is, it is estimated that by continuing our search method in the study area we would eventually reach a total of 28 or 29 morphospecies, about 13% of those known from the island.

It is plain that the two well-vegetated parts of our study area -the savannah and cemetery- contributed disproportionately to this diversity. The rest of the area was a wasteland with respect to ants, with a few samples of Paratrechina sp. A and almost nothing else. This is in line with the common-sense expectation that parks and similar features furnish the greater part of the biodiversity of any city. Gardens (which we did not include) are presumably even more diverse on account of the intentional variety of plants.

 

Table 1. Samples of ants collected during a single day in Port of Spain, Trinidad. Each sample of one or more workers was collected at least five meters from any other. Further explanation in text.

+ = 1-4 samples during the period.

++ = 5 or more samples during the period.

 

Table 1. Samples of ants collected during a single day in Port of Spain, Trinidad.

 

ACKNOWLEDGEMENTS

This study was part of the 5th annual Trinidad and Tobago Bioblitz, chief organiser Mike G. Rutherford.

 

REFERENCES

Bolton, B.Alpert, G.Ward, P.S. and Naskrecki, P. 2007. Bolton's Catalogue of the Ants of the World, 1758-2005. CD-ROM. Cambridge: Harvard Univ. Press.

Gotelli, N.J. and Colwell, R.K. 2011. Estimating species richness. p. 39-54. In A.E. Magurran and B.J. McGill, eds. Biological Diversity: Frontiers of Measurement and Assessment. Oxford: Oxford Univ. Press.

Hölldobler, B. and Wilson, E.O. 1990. The Ants. Cambridge: Harvard Univ. Press 732 p.

Magurran, A.E. 2004. Measuring Biological Diversity. Malden, Massachusetts 256 p.

Philpott, S.M., Perfecto, I., Armbrecht, I. and Parr, C.L. 2010. Ant diversity and function in disturbed and changing environments. p. 137-56. In L. LachC.L. Parr and K.L. Abbott, eds. Ant Ecology. Oxford: Oxford Univ. Press.

Starr, C.K. and Hook, A.W. 2003. The aculeate Hymenoptera of Trinidad, West Indies. Occasional Papers of the Department of Life Sciences, University of the West Indies (12):1-31.

 

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