Abstract
Seed production, quality, germination and seedling establishment are indicators of reproductive success in conifers. Monitoring of these parameters is essential to determine the viability of populations for the purposes of conservation. We analyze cone and seed traits as indicators of reproductive success in the endangered Rzedowski´s pine (Pinus rzedowskii (Madrigal et Caballero) and near-threatened veitchii pine (Pinus ayacahuite var. veitchii (Shaw)) in west-central Michoacán, Mexico. These traits were systematically quantified and their variation assessed using Generalized Linear Mixed Models (GLMMs). We found that the reproductive success of Rzedowski’s pine seems to be critical, presenting low seed efficiency (17.10%), germination (5.0%) and seedling establishment (27.7%), with high levels of inbreeding (0.79). In contrast, veitchii pine presents moderate seed efficiency (54.9%), high germination (71.5%) and seedling establishment (84%–97%) and low inbreeding (0.33). Reproductive indicators differed significantly among zones and populations for each species, where fragment sizes mainly affected seed production and efficiency. This result indicates that fragmentation has played a more important role in the reproductive success of Rzedowski’s pine than in veitchii pine, perhaps by limiting pollen flow among zones and populations and producing higher levels of inbreeding and lower seed efficiency in the former species. We propose a conservation strategy for these important pine species in order to increase their long-term genetic viability.
Highlights
Fragmentation and habitat degradation due to natural disturbance regimes and increasing anthropogenic land use changes have caused the natural populations of plants to become smaller and isolated and subjected to negative genetic and demographic consequences [1,2]
The study areas were divided into zones according to the distribution and population size of each species: three zones for Rzedowski’s pine and two zones for veitchii pine (Figure 1)
The proportions of aborted ovules were very similar in both species, aborted ovules were greater in the second year than in the first year
Summary
Fragmentation and habitat degradation due to natural disturbance regimes and increasing anthropogenic land use changes have caused the natural populations of plants to become smaller and isolated and subjected to negative genetic and demographic consequences [1,2]. Habitat fragmentation promotes a reduction of gene flow between populations, allele loss through the effect of genetic drift and increased levels of inbreeding [2,3,4]. Forests 2016, 7, 178 germination and seedling establishment, Mitton [5]; Nason and Hamrick [6]). This negative effect is present regardless of habitat type, environmental conditions, ecological interactions and life history traits of the species [7,8]. An appropriate evaluation of reproductive indicators is necessary in order to: (i) assess the viability of natural populations; (ii) select regions for seed production; (iii) preserve natural genetic resources; and (iv) develop management and conservation programs for each species
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