Life history adaptations of phyllopods in response to predators, vegetation, and habitat duration in north-eastern Natal

Abstract

Phyllopod populations were monitored in three temporary pools differing in the amount of submerged, peripheral vegetation present, surface area and duration. The effects of these factors on the life history strategies employed by phyllopods were investigated. Triops granarius, various conchostracan species and the anostracan Branchipodopsis sp. inhabited the periphery of two pools where rooted, submerged vegetation was abundant while three Streptocephalus species dominated the central, unvegetated regions of the pools and the unvegetated pool. This distribution pattern appeared to be related to the animals' morphology and feeding habits. The peripheral regions of the pools were stressful habitats since they were colonized by large numbers of predators and competitors 30-40 days after inundation and they dried out sooner than the centre. The 'peripheral' species exhibited typical r-selected life history strategies; they grew rapidly, reproduced early and had short lifespans and in this way they overcame the threats presented by their habitat. The 'central' species took advantage of their predator-free, more stable habitat and exhibited life history patterns which tended towards the K-end of the r-K continuum. A degree of intraspecific variation in growth and reproduction was obvious and appeared to be related to differences in habitat duration of the three pools,

Distribution and assemblages of large branchiopods (Crustacea: Branchiopoda) of northern Western Ghats, India

“…All combinations of species of the three orders of large branchiopods were seen recurring over studied area, especially on rocky outcrops. Similar recurring assemblages of different orders have been reported from USA, Mexico and Africa (Hamer and Appleton, 1991b;Thiéry, 1991;Maeda-Martínez et al, 1997). Triops granarius, in the current study was observed only in assemblages, an observation also noted for the congeneric species T. cancriformis (Petrov and Cvetković, 1997;Boven et al, 2008;Waterkeyn et al, 2009).…”

Species richness, endemism and ecology of crustacean assemblages in northern California vernal pools

“…First, short-lived pools may lack some species because they dry up before species with a long period of development can complete their life cycles, while pools of longer duration provide habitat for both rapidly and slowly developing species (Hamer & Appleton, 1991 ;Hammer & Sawchyn, 1968 ;Retallack & Clifford, 1980;Simovich & Fugate, 1992 ;Thiery, 1991 ;Wiggins et al ., 1980) . Studies of developmental rates under natural temperature and food regimes for the numerous species that are found only in large, deep pools would help to test the hypothesis that these species are unable to inhabit short-lived pools due to developmental time constraints .…”

“…Similar cases of temporal separation of species in the same pool are known for other anostracan species (Eng et al ., 1990 ;Simovich & Fugate, 1992 ;Simovich & Hathaway, unpublished data) . Third, large, deep pools may hold more species because they have greater habitat heterogeneity (sensu Williams, 1964) which allows for more niches and greater resource partitioning (Daborn, 1978 ;Hamer & Appleton, 1991 ;Thiery, 1991) . Some evidence for greater habitat heterogeneity in large pools is provided by the zonation of vernal pool plants : in large, deep pools vernal pool plants form concentric rings from the edge to the pool center, each ring being dominated by the species that is best suited for that microhabitat ; in contrast, small, shallow pools are carpeted by only 'edge-adapted' species (Zedler, 1987) .…”

“…Also, deep pools contain open water columns, whereas the proximity of bottom and surface in shallow pools which are only a few centimeters deep precludes this type of microhabitat . Support for such a habitat heterogeneity hypothesis comes from many aquatic and terrestrial systems (Huston, 1979), including birds (MacArthur & MacArthur, 1961), cladocerans (Armitage & Davis, 1967 ;Quade, 1969 ;Whiteside & Harmsworth, 1967), eubranchiopods (Hamer & Appleton, 1991 ;Thiery, 1991), and crustacean assemblages (Anderson, 1974) . An hypothesis of increasing species richness with increasing habitat complexity does not completely account for patterns of species richness in all systems, however (Fryer, 1985) .…”

Seasonal changes in the invertebrate community of small shallow ephemeral pans at Bain's Vlei, South Africa

“…In and regions temporary water communities are characterized by those crustacean orders collectively known as phyllopods (Hutchinson, 1931 ;Rz6ska, 1961 ;Weir, 1969 ;Coetzer, 1981 ;Williams, 1985 ;Seaman & Kok, 1987) . They are the Conchostraca (alternatively classified as two separate orders Spinicaudata and Laevicaudata, Fryer, 1987a) Anostraca and Notostraca, and several species in each order have been found coexisting in the same waterbody (Donald, 1983 ;Brendonck, Thiery & Coomans, 1990 ;Hamer & Appleton, 1991 ;Thidry, 199 1) . They are rare in permanent waters and are frequently referred to as`temporary water taxa' .…”