Abstract
Land degradation and soil erosion in the upper catchments of tropical lakes fringed by papyrus vegetation can result in a sediment load gradient from land to lakeward. Understanding the dynamics of clonal modules (ramets and genets) and growth strategies of plants on such a gradient in both space and time is critical for exploring a species adaptation and processes regulating population structure and differentiation. We assessed the spatial and temporal dynamics in clonal growth, diversity, and structure of an emergent macrophyte, Cyperus papyrus (papyrus), in response to two contrasting sedimentation regimes by combining morphological traits and genotype data using 20 microsatellite markers. A total of 636 ramets from six permanent plots (18 x 30 m) in three Ethiopian papyrus swamps, each with discrete sedimentation regimes (high vs. low) were sampled for two years. We found that ramets under the high sedimentation regime (HSR) were significantly clumped and denser than the sparse and spreading ramets under the low sedimentation regime (LSR). The HSR resulted in significantly different ramets with short culm height and girth diameter as compared to the LSR. These results indicated that C. papyrus ameliorates the effect of sedimentation by shifting clonal growth strategy from guerrilla (in LSR) to phalanx (in HSR). Clonal richness, size, dominance, and clonal subrange differed significantly between sediment regimes and studied time periods. Each swamp under HSR revealed a significantly high clonal richness (R = 0.80) as compared to the LSR (R = 0.48). Such discrepancy in clonal richness reflected the occurrence of initial and repeated seedling recruitment strategies as a response to different sedimentation regimes. Overall, our spatial and short-term temporal observations highlighted that HSR enhances clonal richness and decreases clonal subrange owing to repeated seedling recruitment and genets turnover.
Highlights
Clonality is a widespread life history trait in angiosperms that maximizes plant fitness [1, 2] and is significant for population persistence under a heterogeneous and stochastic environment [3, 4, 5]
In this study, combining clonal traits and genetic data, we found a trade-off between phalanx strategy and guerrilla strategy under contrasting sedimentation regimes
Higher levels of sedimentation led to an increase in ramet density, enhanced phalanx strategy and favored higher clonal diversity which can be ascribed to seedling recruitment
Summary
Clonality is a widespread life history trait in angiosperms that maximizes plant fitness [1, 2] and is significant for population persistence under a heterogeneous and stochastic environment [3, 4, 5]. RSR strategy enables survival of small clones of different age and size to coexist and leads to high genetic and clonal diversity within a population [19]. Differential intensity between these recruitment strategies dictates clonal richness [19, 20] and contributes to patch growth, clone coexistence and evolution, and disturbance recovery [18, 21]. In examining the populations of a species occurring in different environments, it is important to explore how each reproduction mode and recruitment strategy contributes to genets distribution and dynamic
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