“No signs of saturation”: long-term dynamics of vascular epiphyte communities in a human-modified landscape

Einzmann, Helena J. R.; Zotz, Gerhard

doi:10.1007/s10531-017-1306-z

Cited by 26 publications

(57 citation statements)

References 58 publications

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“…Compared to tropical epiphyte communities (Einzmann & Zotz, ; Laube & Zotz, , ), the species composition and species abundance of observed epiphytic individuals in this study differed much more between study years, as indicated by a lower Jaccard index and lower Bray–Curtis index (Table ). Even though observation intervals were much longer, temporal fluctuations of these tropical epiphyte communities were smaller.…”

Section: Discussioncontrasting

confidence: 56%

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Accidental epiphytism in the Harz Mountains, Central Europe

Hoeber

Weichgrebe

Zotz

2019

J Vegetation Science

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Questions: Vascular epiphytes make up about 9% of all vascular plants globally but are clearly underrepresented in the temperate zones. The accidental epiphytic occurrence of terrestrial species, in contrast, is common at these latitudes and can provide important insights in the evolution of obligate epiphytes. Here, we present the results of the first two annual censuses of a planned long-term study on accidental epiphytes. We particularly aim to identify: (a) the abundance and species richness of accidental epiphytes; (b) the dynamics of accidental epiphytism; (c) occupied substrates and microsites; and (d) suitable host tree species. Location: Harz Mountains, Germany, Central Europe. Methods: We surveyed more than 1,200 trees in a low mountain range in two consecutive years for epiphytic individuals of vascular plants, considering host tree species and occupied microsites. Results: About one quarter of the surveyed trees hosted epiphytic plants, totalling 1 450 (2016) and 1 350 (2017) individuals, respectively. These belonged to more than 100 species and 39 different families. The majority of epiphytic individuals newly emerged in 2017, whereas one-third persisted since 2016 (or earlier) and a smaller proportion even reproduced in the epiphytic habitat. Accidental epiphytes were mostly restricted to host tree species providing water-storing substrates such as extensive moss pads or arboreal soil accumulated in crotches. Compared to tropical epiphyte communities, accidental epiphytes in the temperate zones show a higher turnover, as they are less consistent in species abundance and composition in time.Conclusion: For the majority of the observed species, epiphytism indeed is an accidental phenomenon. Undoubtedly, abiotic conditions limit the occurrence of obligate epiphytes at higher latitudes, but the presence and persistence of numerous epiphytic individuals illustrate that abiotic conditions do not per se preclude epiphytic occurrence of vascular plants in the north-temperate zone. Besides water shortage, the availability of suitable host trees is a decisive environmental factor that contributes to limit epiphytism of vascular plants in Central Europe.

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Section: Discussioncontrasting

confidence: 56%

“…For the calculation of the indices, only unambiguously identified species or morphospecies were included. These indices were also calculated for three other studies with repeated epiphyte censuses in the tropics (namely Einzmann & Zotz, ; Laube & Zotz, , ).…”

Section: Methodsmentioning

confidence: 99%

Accidental epiphytism in the Harz Mountains, Central Europe

Hoeber

Weichgrebe

Zotz

2019

J Vegetation Science

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“…Likewise, disturbance has marked negative effects on the diversity and composition of the phorophyte community (Quesada et al 2009; Munguía-Rosas and Montiel 2014), and in microclimatic conditions (Laurance 2004), which are critical for the survival of epiphytic species in dry forest habitats. Studies on epiphytic plants show contrasting results: some have found lower diversity but higher recruitment in secondary cloud forests (Cascante-Marín et al 2006), or lower seedling establishment on isolated trees than in old-growth forests (Werner and Gradstein 2008), while other studies show that some rainforest epiphytes actually increase in abundance in human-modified environments (Einzmann and Zotz 2017). Nevertheless, for epiphytes that depend on trees with particular characteristics, such as dry forest Tillandsia species, the reduction in the abundance of appropriate phorophytes affects the recruitment of new plants and possibly the long-term viability of epiphyte populations (Sáyago et al 2013).…”

Section: Discussionmentioning

confidence: 99%

Consequences of Habitat Fragmentation on the Reproductive Success of two Tillandsia species with Contrasting Life History Strategies

et al. 2018

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Fragmentation of natural habitats generally has negative effects on the reproductive success of many plant species; however, little is known about epiphytic plants. We assessed the impact of forest fragmentation on plant–pollinator interactions and female reproductive success in two epiphytic Tillandsia species with contrasting life history strategies (polycarpic and monocarpic) in Chamela, Jalisco, Mexico, over three consecutive years. Hummingbirds were the major pollinators of both species and pollinator visitation rates were similar between habitat conditions. In contrast, the composition and frequency of floral visitors significantly varied between habitat conditions in polycarpic and self-incompatible T. intermedia but not in monocarpic self-compatible T. makoyana. There were no differences between continuous and fragmented habitats in fruit set in either species, but T. makoyana had a lower seed set in fragmented than in continuous forests. In contrast, T. intermedia had similar seed set in both forest conditions. These results indicate that pollinators were effective under both fragmented and continuous habitats, possibly because the major pollinators are hummingbird species capable of moving across open spaces and human-modified habitats. However, the lower seed set of T. makoyana under fragmented conditions suggests that the amount and quality of pollen deposited onto stigmas may differ between habitat conditions. Alternatively, changes in resource availability may also cause reductions in seed production in fragmented habitats. This study adds to the limited information on the effects of habitat fragmentation on the reproductive success of epiphytic plants, showing that even related congeneric species may exhibit different responses to human disturbance. Plant reproductive systems, along with changes in pollinator communities associated with habitat fragmentation, may have yet undocumented consequences on gene flow, levels of inbreeding and progeny quality of dry forest tillandsias.

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“…In both cases, we could take advantage of detailed earlier studies. In the first case, Zotz & Schultz (2008) had monitored 13,000 vascular epiphyte individuals in 0.4 ha, providing detailed information on their vertical distributions within the forest, in the second case, Einzmann & Zotz (2017) had recorded all epiphytes in 622 pasture trees. Finally, in order to assess how much intraspecific variation in root morphology may be hidden when species averages are used, we quantified differences in three species with a wide distributional range along the regional rainfall gradient.…”

Section: Introductionmentioning

confidence: 99%

Variation in root morphology of epiphytic orchids along small-scale and large-scale moisture gradients

2020

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Root morphology is expected to respond to environmental conditions. Two earlier studies reported predictable changes in the structure of the velamen radicum (common in monocotyledons) along rainfall gradients, which was expected from its assumed role in plant-water-relations. The present study expanded on this idea by analysing nine root traits that can be linked to root function, including velamen structure, along two moisture gradients of different spatial scales: 1) along the vertical gradient of a lowland forest in central Panama and 2) along a strong regional rainfall gradient in western Panama. All studied traits (e.g. velamen width, number of xylem poles, lignification of the exodermis) of the 45 orchid species showed substantial intraspecific and interspecific variation, but none of this (within forest) or very little of this (regional gradient) was related to the gradients. Only the community weighted means of velamen width, stele width and xylem pole number varied significantly with rainfall, with substantial effect sizes only found in the latter two traits. Our results clearly disagree with those of earlier publications, which did not include species abundance and/or rigorous statistics in their analyses. This discrepancy highlights that our understanding of the link between velamen form and function is still rudimentary.

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“No signs of saturation”: long-term dynamics of vascular epiphyte communities in a human-modified landscape

Cited by 26 publications

References 58 publications

Accidental epiphytism in the Harz Mountains, Central Europe

Accidental epiphytism in the Harz Mountains, Central Europe

Consequences of Habitat Fragmentation on the Reproductive Success of two Tillandsia species with Contrasting Life History Strategies

Variation in root morphology of epiphytic orchids along small-scale and large-scale moisture gradients

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