Reproductive ecology and inbreeding depression inOpuntia rastrera(Cactaceae) in the Chihuahuan Desert: Why are sexually derived recruitments so rare?

Abstract

We evaluated the influence of the reproductive ecology on low recruitment of sexually derived progeny observed in Opuntia rastrera Weber in the Southern Chihuahuan Desert, in two vegetation types. The flowers are diurnal, remaining open 9–10 hr. Pollen is released in the morning and at the same time the stigmas become receptive. Nectar is produced all day, but the production rate is higher at noon. The flowers are visited by insects, mainly solitary bees (Diadasia sp. and Lithurge sp.). Floral characteristics and the pollen/ovule ratio suggest that Opuntia rastrera is a facultative xenogamous species. Controlled pollinations indicate that it is not apomictic and pollinators are required to set fruit; it is also self‐compatible, but there is strong inbreeding depression for fruit set. However, we were unable to demonstrate differences in reproductive characters between the populations in both vegetation types. The average density of adults per hectare was one order of magnitude higher in the nopalera (Opuntia‐dominated scrublands) than in the grassland. However, the average density of plants that originated from seeds was one order of magnitude lower in the nopalera. Opuntia rastrera produces abundant flowers, fruits, and seeds in both vegetation types in natural conditions. The low success in the recruitment of new genets cannot be ascribed to the reproductive ecology.

Spatial Associations, Size–Distance Relationships and Population Structure of Two Dominant Life Forms in a Semiarid Enclave of the Venezuelan Andes

“…Asexual reproduction in many arid-land succulent species can be a consequence of a very low production of viable seeds or can be related to environmental bottlenecks that drastically reduce the establishment of seedling (Franco and Nobel 1989;Mandujano et al 1996). Both aspects have been scarcely evaluated in the semiarid environments of the Venezuelan Andes (Sosa and Soriano 1996;Soriano and Ruiz 2002).…”

Reproductive biology of a highly endemic species: Cipocereus laniflorus N.P. Taylor & Zappi (Cactaceae)

“…124 genera and around 1500 species distributed almost exclusively within the American Continent, with major centres of diversity in the arid regions of Mexico, central Andes (Argentina and Bolívia) and Eastern Brazil (Barthlott & Hunt 1993;Hunt et al 2006;Taylor & Zappi 2004). Floral characters, such as colour, size, position of reproductive structures and time of anthesis are very diverse, and the species present a large array of pollination syndromes (see Faegri & Van der Pijl 1979) and several groups of invertebrates and vertebrates have been observed as visitors and pollinators, such as bees Mandujano et al;, beetles (Grant & Connell 1979), hawkmoths (Silva & Sazima 1995;Locatelli & Machado 1999a), birds and bats (Alcorn et al 1961, McGregor et al 1962Locatelli & Machado 1999b;Aona et al 2006;Rocha et al 2007).…”

<htm>Visitantes florais de <i>Opuntia monacantha </i>(Cactaceae) em restingas de Florianópolis, SC, Brasil</htm>

“…Em geral, existe um consenso sobre o papel limitado de coleópteros na polinização de Opuntia spp. (GRANT & CONNELL, 1979;DEL CASTILLO & GONZALEZ, 1988;MCFARLAND et al, 1989;MANDUJANO et al, 1996 ;REYS-AGÜERO et al, 2006) AGRADECIMENTOS -Ao Profº Clemens Schlindwein (Dept. Botânica/UFPE) pela identificação de Cephalocolletes isabelae; ao Profº Benedito C. Lopes (CEZ/UFSC) pela identificação das formigas; ao Fabiano F. Albertoni (CEZ/UFSC) pela confirmação de Camptodes sp.…”