LIFE-HISTORY STRATEGIES AMONG BRYOPHYTES OF ARID REGIONS

Abstract

  Three life-history strategies predominate among hot-desert bryophytes: 1. Perennial stayers are represented by acrocarpous mosses with long-lived, desiccation-tolerant gametophytes, small spores, long setae and other features promoting dispersal; 2. Annual shuttle species include ephemeral mosses and liverworts that practice drought evasion, developing rapidly after rain and producing large spores, often in immersed capsules; 3. Perennial shuttle species, mainly marchantioid hepatics, combine desiccation tolerant gametophytes with large spores. Colonists are prominent in places in Spanish mediterranean regions, where Funaria hygrometrica, a fugitive, is locally abundant in burnt woodland. Fugitives are generally prominent for only 1-2 years at a given site. They and colonists are believed to migrate between sites as small, easily-dispersed spores, or in some colonists as asexual propagules. It is stressed that current concepts regarding both phyletic and functional aspects of bryophyte life-history strategies are highly speculative, but a comparison of spore output and reproductive effort in Funaria hygrometrica and a perennial stayer confirmed that the former has many attributes to be anticipated in species acting as fugatives.