Better alone? A demographic case study of the hemiparasite Castilleja tenuiflora (Orobanchaceae): A first approximation

Abstract

Castilleja tenuiflora is a facultative root hemiparasitic plant that has colonized a disturbed lava field in central Mexico. To determine the effects of hemiparasitism on the population dynamics of the parasite, we identified a set of potential hosts and quantified their effects on the vital rates of C. tenuiflora during 2016–2018. Connections between the roots of the hemiparasite and the hosts were confirmed with a scanning electron microscope. Annual matrices considering two conditions (with and without potential hosts) were built based on vital rates for each year, and annual stochastic finite rate growth rates (λs) were calculated. Plants produced more reproductive structures with hosts than without hosts. A Life Table Response Experiment (LTRE) was performed to compare the contributions of vital rates between conditions. We identified 19 species of potential hosts for this generalist hemiparasite. Stochastic lambda with hosts λs = 1.02 (CI = 0.9999, 1.1) tended to be higher than without them λs = 0.9503 (CI = 0.9055, 0.9981). The highest elasticity values correspond to survival. LTRE indicated that the most important parameters are survival and fecundity; the total contribution of fecundity (0.0192) to the difference in growth was three times lower than that of survival (0.0603). Piqueria trinervia was the most abundant host, and C. tenuiflora had a higher lambda with it than with other species. Individuals can grow alone, but hosts can have a positive effect on the vital parameters of C. tenuiflora and on λ.

Estimation of demographic parameters of some plant species accounting for imperfect detection probabilities

“…In the case of F. chlorifolia , which had low and variable values of p , sampling was complicated because individuals are established into cracks or sinkholes, whose size can vary in width, depth, and plant diversity (Peralta‐García et al, 2016). On the other hand, individuals of C. tenuiflora , which had high and constant values of p , are established on flat lands in sites that are easily accessible (Granados‐Hernández et al, 2021).…”

“…Underestimation of survival probabilities due to imperfect detection of individuals during field surveys could lead to wrong conclusions about the population status (Alexander et al, 2009; Kéry & Gregg, 2003; Shefferson et al, 2001) or evolutionary trends of plant species (e.g., in studies that aim to quantify the strength of natural selection; Waller & Svensson, 2016). The consequences can be serious, especially if the research is focused on rare or endangered species (such as M. hernandezii , N. macrocephala , and G. lagenophora ; Esparza‐Olguín et al, 2005; Ureta & Martorell, 2009), species that act as indicators of environmental change (such as F. chlorifolia ; Pisanty et al, 2020; Rodríguez‐Sánchez et al, 2020), or species that support biotic interactions (such as C. tenuiflora which is a hemiparasitic plant; Granados‐Hernández et al, 2021).…”

“…Based on previous knowledge about the life cycle and reproductive phenology of each species (Esparza‐Olguín et al, 2005; Granados‐Hernández et al, 2021; Pisanty et al, 2020; Rodríguez‐Sánchez et al, 2020; Ureta & Martorell, 2009), as well as on field observations, we constructed life cycle graphs for the five species (a general life cycle graph is depicted in Figure 1a and species‐specific life cycle graphs for all five species are shown in Figures S1–S5). From one sampling occasion to the next, individuals can survive with state‐specific probability S , and if they survive, they can make a transition to a different state or size class (i.e., transitions in strict sense: ψ AB , ψ BA , ψ BC , ψ CB , ψ CA , and ψ AC in Figure 1a) or, alternatively, they can remain in the same state or size class (i.e., stasis: ψ AA , ψ BB , and ψ CC in Figure 1a).…”

“…Several factors can cause imperfect detection of plants, including particular phenotypic traits of each species (life form, phenology, size, shape, coloration), intensity of sampling effort, and numerous habitat characteristics, both biotic (density, height, or phenological pattern of the surrounding vegetation) and abiotic (topography, type of substrate). For example, our two perennial herbs (F. chlorifolia and C. tenuiflora) grow immersed within vegetation with a similar height or phenological pattern (Cervantes-Campero et al, 2020;Granados-Hern andez et al, 2021;Mendoza-Hern andez et al, 2013;Peralta-García et al, 2016). Additionally, the aerial tissue of both species is susceptible to breaking, especially in dry individuals.…”

Parasitic Plants as Vectors for Pathogens

“…However, host specificity is largely determined by the extent of reliance on the host plant and depends on the ability of the haustoria to functionally establish after invading the host. The most common potential hosts are from Asteraceae, Cyperaceae, Fabaceae, Labiatae, Poaceae and Rosaceae families [42,43]. In general, facultative parasites, specially root hemiparasites, have a broad host range, whereas obligate/shoot parasites tend to be more host-specific [44].…”