DOI: 10.5061/dryad.44j0zpc8x
title: Propagule composition regulates the success of an invasive seaweed across a heterogeneous seascape

description: 1. Propagule pressure is acknowledged as a key determinant of invasion
 success. Nonetheless, the role of morphological or physiological
 attributes of propagules (i.e., their quality) in regulating invader
 establishment has been little explored. In particular, no study has
 investigated how the presence of propagules differing in quality within an
 inoculum influences establishment across heterogeneous landscapes. 2. We
 experimentally tested the hypothesis that the quality (+Fronds+Rhizoids;
 +Fronds–Rhizoids; –Fronds+Rhizoids) and the diversity (1, 2, 3 fragment
 types) of vegetative fragments of the seaweed Caulerpa taxifolia determine
 their establishment success across seascapes consisting of bare sediments
 and patches of the seagrass Zostera muelleri exposed to different
 disturbance intensities (control, seagrass canopy clipping and total
 removal). 3. After 6 weeks, seaweed biomass, stolon and frond length,
 frond and rhizoid number were generally greater in unvegetated habitats
 (bare sediments and total seagrass removal) than full or reduced seagrass
 canopies. The type and the diversity of types of fragments inoculated had
 significant effects on the final biomass and morphological features of C.
 taxifolia only in vegetated habitats. In control plots, inocula of
 fragments retaining both fronds and rhizoids achieved higher biomass,
 developed longer stolons and more fronds. In canopy clipping plots, mixed
 inocula of +Fronds+Rhizoids and –Fronds+Rhizoids fragments had the
 greatest biomass and stolon length. 4. Synthesis. Assessing how propagules
 differing in quality perform in different habitats might be not sufficient
 to draw a comprehensive picture of invasion risk, as their establishment
 can be modulated by both negative and positive interactions among them.
 Propagule composition should be, therefore, considered as a further
 dimension of propagule pressure. Our results also suggest that the
 relevance of specific propagule traits for invader establishment decreases
 from intact to degraded habitats. Considering propagule size in terms of
 amount of competent propagules, rather than an absolute measure, would
 refine our ability of predicting invasion risk across habitats differing
 in biotic or abiotic conditions.
description: This dataset was generated by a field experiment. Data have been
 analyzed by means of ANOVA techniques.
description: The dataset is composed by two Excel worksheets. Data on the
 Total dry weight of<em> Caulerpa taxifolia</em> are reported
 in the first sheet (named Total dry weight). Data on Total stolon
 length, Rhizoid number, Leaf number and Mean frond length are reported in
 the second sheet (named Morphometric measures). Missing values (see paper
 for details) are omitted from the dataset. The
 different types of fragments of <em>Caulerpa taxifolia</em>
 are coded as follows under the column "Fragment Type":
 A = fragments with both fronds and rhizoids (+F +R)
 B = fragments with fronds and without rhizoids  (+F -R)
 C = fragments without fronds and with rhizoids (-F +R)