Background:

Understanding changes in local community composition along environmental gradients is essential for studying the long-term metacommunity dynamics. The metacommunity structure depends on the distribution of species along environmental gradients in terms of their coherence (continuity in their distribution range), species turnover and grouping of their range limits. A Clementsian structure would be defined by coherent ranges, significant turnover and sharp limits between local communities. All other things equal, a Gleasonian structure is distinguished by the absence of clear boundaries between local communities.

Questions:

The structure of a scrubland/semiarid/xeric metacommunity changes 23 years after its first characterization? Do environment and spatial variables determine the metacommunity structure?

Species studied:

104 perennial-plant species.

Study site and dates:

Zapotitlán semi-arid valley, Puebla, in 1980 and 2003.

Methods:

Metacommunity structure and its relationship to environmental (edaphic) and spatial (altitude, slope and geographical location) variables were analyzed using data from the two historic surveys.

Results:

In 1980 a Clementsian structure was determined, which remained unchanged after 23 years. The importance of environmental filters decreased from 1980 to 2003.

Conclusions:

The prediction that, due to stochastic dispersion of propagules, the metacommunity would tend toward a Gleasonian structure was not fulfilled. There was no evidence for homogenization, although local tetechera communities (with dominance of the giant columnar cactus Cephalocereus tetetzo) had been invaded and transformed into shrubland communities. Local communities and the metacommunity should be monitored continuously to understand of the long-term structuration of these systems.