Haploid females in the isomorphic biphasic life-cycle of Gracilaria chilensis excel in survival

Abstract

BackgroundConditional differentiation is one of the most fundamental drivers of biodiversity. Competitive entities (usually species) differ in environmental or ecological niche enabling them to co-exist. Conditional differentiation of haploid and diploid generations is considered to be a requirement for the evolutionary stability of isomorphic biphasic life-cycles and the cause for the natural occurrence of both phases at uneven abundances. Theoretically, stage dependent survival rates are the most efficient way to explain conditional differentiation.ResultsWe tested for conditional differentiation in survival rates among life stages (haploid males, haploid females, and diploids) of Gracilaria chilensis, an intertidal red alga occurring along the Chilean shores. Therefore, the fate of individuals was followed periodically for 3 years in five intertidal pools and, for the first time in isomorphic red algae, a composite model of the instantaneous survival rates was applied. The results showed the survival dependency on density (both competition and Allee effects), fertility, age, size, season and location, as well as the differentiation among stages for the survival dependencies of these factors. The young haploid females survived more than the young of the other stages under Allee effects during the environmentally stressful season at the more exposed locations, and under self-thinning during the active growth season. Furthermore, fertile haploid females had a higher survival than fertile haploid males or fertile diploids.ConclusionsHere, we show a survival advantage of haploids over diploids. The haploid females probably optimize their resource management targeting structural and physiological adaptations that significantly enhance survival under harsher conditions. In a companion paper we demonstrate a fertility advantage of diploids over haploids. Together, the survival and fertility differentiation support the evolution and prevalence of biphasic life-cycles.Electronic supplementary materialThe online version of this article (10.1186/s12862-018-1285-z) contains supplementary material, which is available to authorized users.

Differential Frond Growth in the Isomorphic Haploid–diploid Red Seaweed Agarophyton chilense by Long‐term In Situ Monitoring

“…Desiccation and UV exposure were particularly harsh at Corral 2, with fronds experiencing high mortalities (Vieira et al. 2018a). Sampling occurred from October 2009 to February 2012 at 4‐month intervals.…”

“…2013, Vieira et al. 2018a,b, Bellgrove and Aoki 2020). Besides direct observations, indirect evidence supporting conditional differentiation has also emerged.…”

“…2018) showed that, under stressful conditions demanding specific and efficient resource allocation, adult haploid females had a higher survival than adult diploids (Vieira et al. 2018a) while the adult haploid males showed increased fecundity compared to any other stage (Vieira et al. 2018b).…”

“…Furthermore, it was also observed that diploid germlings had a higher survival than haploid germlings (Vieira et al. 2018a), most likely due to maternal care by the haploid females passing resources on to their diploid progeny (Kamiya and Kawai 2002). All together, these observations suggest that a resource limitation hypothesis may justify both a haploid advantage on the adults (directly) and a diploid advantage on the sporelings (indirectly, through haploid maternal care).…”

A model for the biomass–density dynamics of seagrasses developed and calibrated on global data

“…Following the bulk literature on biomass–density relations, the biomass (B in g DW m −2 ) and density (D in shoots m −2 ) were replaced by b = log 10 B and d = log 10 D. Coincidently, these correspond to instantaneous rates (although traditionally use the e base), allowing the application of linear algebra to non-linear processes, and thus standardizing per day (i.e., ∆b/∆t and ∆d/∆t) growth rates that in their original studies related to quite different time intervals. This advantage of instantaneous over finite rates has made them the most suited for studies in fisheries [30, 31] and evolutionary [32, 33] ecology.…”