Diaspore heteromorphism in the invasive Bromus tectorum L. (Poaceae): Sterile florets increase dispersal propensity and distance

Abstract

Please cite this article as: Monty, Arnaud, Maebe, Laura, Mahy, Grégory, Brown, Cynthia S., Diaspore heteromorphism in the invasive Bromus tectorum L.(Poaceae): sterile florets increase dispersal propensity and distance.Flora http://dx.doi.org/10.1016/j.flora. 2016.06.004 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.  Bromus tectorum is a troublesome invasive grass in North America.  The sterility of terminal florets induces a diaspore heteromorphism.  Dispersal of diaspores with and without sterile florets attached was investigated.  Primary and secondary dispersal by biotic and abiotic agents were considered.  Across the study, diaspores with sterile florets were better dispersers. 2 AbstractWithin a species, the distance travelled by a particular diaspore depends on its morphology. In Poaceae, the presence of terminal sterile florets can lead to diaspore heteromorphism, which may influence dispersal. We tested the hypothesis that the presence of sterile florets favored dispersal in Bromus tectorum L., an invasive grass in the Western US.We used field and controlled experiments to study the dispersal of caryopses with and without sterile florets attached (respectively complex and simple diaspores), as well as pieces of inflorescence that detached from the mother plants. We considered both primary and secondary dispersal, as well as abiotic and biotic dispersal agents. The distance travelled by the diaspores and their attachment to animal fur were related to the presence and number of sterile florets.Abiotic agents moved diaspores over relatively short distances, both in terms of primary and secondary dispersal. A significant proportion of diaspores attached to fur, suggesting a potential for dispersal over longdistances. Complex diaspores were better dispersers than simple ones (and pieces of inflorescence), and this pattern was consistent across the study. However, among complex diaspores, the number of sterile florets had little or no influence.Considering primary and secondary dispersal by abiotic and biotic agents provided a general picture of the dispersal ecology of B. tectorum. For all the dispersal steps and dispersal agents we studied, the presence of sterile florets favored dispersal. These results highlight the functional significance of diaspore heteromorphism induced by floret sterility in the dispersal of Poaceae.

Intrinsic and extrinsic drivers of intraspecific variation in seed dispersal are diverse and pervasive

“…The most apparent cases of morphology driving interindividual variation in seed dispersal are with heterocarpic species that produce diaspores of two or more distinct morphologies differing in dispersal ability. For example, in the annual grass Bromus tectorum plants produce caryopses with (complex) and without (simple) sterile florets attached, which differ in dispersal ability because complex diaspores attach better to animal fur (Monty et al 2016). Numerous plant species produce dimorphic, soft (non-dormant) and hard (dormant) seeds (Baskin and Baskin 2014).…”

Consequences of intraspecific variation in seed dispersal for plant demography, communities, evolution and global change

“…However, mixed evidence for evolutionary change in seed dispersal has been found for range expansions under field conditions (e.g. Bartle et al 2013; Huang et al 2015; Monty et al 2016), which require further study.…”

“…pulp to seed ratio or elaisome size) result in higher removal probabilities (Sallabanks 1993; Willson 1994; Mark and Olesen 1996; Stanley and Lill 2002). For fruit dispersed by epizoochory, there is variation in the presence, size and number of appendages that enable mechanical interlocking with animal fur (Gorb and Gorb 2002) or variation in the degree of heterocarpy, in which individual plants produce morphologically distinct diaspores (Monty et al 2016). However, the impact of this variation on dispersal has not yet been tested for this dispersal mode.…”

Philomatry in plants: why do so many species have limited seed dispersal?

“…The hooks, barbs, and awns useful to adhesive dispersal by animals (Sorensen, 1986) involve at least a small physiological cost. In the invasive grass Bromus tectorum L., maternal plants produce complex diaspores with entire awned, sterile florets clustered in a group (the energy cost) along with a fertile floret containing a single caryopsis to enhance adhesive dispersal on mammalian fur (Monty et al, 2016).…”