• Cover image
    Issue
    Volume 101, Issue 3
    545-836
    May 2013

SPECIAL FEATURE: NEW PERSPECTIVES IN WHOLE‐PLANT SENESCENCE

Special Feature – Future Directions No. 8

Open Access

Plants do not count… or do they? New perspectives on the universality of senescence

  • Pages: 545-554
  • First Published:24 April 2013

Understanding the conditions under which senescence has evolved is of general importance across biology, ecology, evolution, conservation biology, medicine, gerontology, law and social sciences. The question ‘why is senescence universal or why is it not?’ naturally calls for an evolutionary perspective. Senescence is a puzzling phenomenon, and new insights will be gained by uniting methods, theories and observations from formal demography, animal demography and plant population ecology. Plants are more amenable than animals to experiments investigating senescence, and there is a wealth of published plant demographic data that enable interpretation of experimental results in the context of their full life cycles. It is time to make plants count in the field of senescence.

Special Feature – Standard Papers

Free Access

Photo‐oxidative stress markers reveal absence of physiological deterioration with ageing in Borderea pyrenaica, an extraordinarily long‐lived herb

  • Pages: 555-565
  • First Published:24 April 2013

Neither males nor females of the extraordinarily long‐lived Borderea pyrenaica show age‐dependent signs of oxidative stress. This observation suggests that age‐induced oxidative stress is not a universal feature of ageing in perennial plants. Indeed, females older than 100 years showed signs of negative senescence, in that they registered improved physiological performance with increasing age.

Free Access

Prolonged dormancy interacts with senescence for two perennial herbs

  • Pages: 566-576
  • First Published:24 April 2013

We develop a modelling framework for how prolonged dormancy may affect senescence in perennial plants. Using this framework for long‐term demographic data from two perennial herbs, the present study shows mixed evidence for senescence in perennial plants. Our results indicate that prolonged dormancy interacts with the age‐dependence of vital rates and may sometimes retard the process of senescence.

Free Access

Longitudinal analysis in Plantago: strength of selection and reverse age analysis reveal age‐indeterminate senescence

  • Pages: 577-584
  • First Published:24 April 2013

The hypothesis that plants escape senescence generally assumes that plants can continue to grow larger and increase reproduction as they get older. The results here show that size and reproduction decline with age and the rates of these declines toward death are lifespan‐ and age‐dependent. Further research is needed to delineate the importance of age‐determinate vs. age‐indeterminate factors in senescence patterns across species.

Open Access

Age, stage and senescence in plants

  • Pages: 585-595
  • First Published:24 April 2013

Theories for the evolution of senescence focus on the decline with age in the magnitude of the selection gradient on age‐specific mortality. This decline implies that mortality late in life has less impact on fitness than mortality early in life. The demography of plants, however, often depends on size or stage rather than on age alone. We develop an age‐stage classified model and show that in such a population the selection gradient on mortality may increase, rather than decrease, with age within a stage, leading to contra‐senescent selection.

Free Access

The pace and shape of senescence in angiosperms

  • Pages: 596-606
  • First Published:24 April 2013

Frequency distribution of shape values for different growth forms. The dashed gray vertical line marks the boundary of senescence. Below this point, species show negative senescence, at that point species show negligible senescence and above that point species show senescence.

Invasion ecology

Free Access

Pathogen accumulation and long‐term dynamics of plant invasions

  • Pages: 607-613
  • First Published:06 March 2013

Here we briefly review the patterns and potential mechanisms of pathogen accumulation on invasive plant species and outline the primary needs for future research. We provide conceptual models to describe the potential outcomes of pathogen accumulation for invasive and resident native species and describe observational, experimental, and modeling research approaches.

Determinants of plant community diversity and structure

Free Access

Large herbivores favour species diversity but have mixed impacts on phylogenetic community structure in an African savanna ecosystem

  • Pages: 614-625
  • First Published:13 March 2013

Extinction of large mammal herbivores will have cascading effects on plant diversity; however, impacts on plant community structure are contingent on initial conditions. This research has implications for best practice when managing large herbivores and natural habitats.

Free Access

Fine‐scale spatial patterns in grassland communities depend on species clonal dispersal ability and interactions with neighbours

  • Pages: 626-636
  • First Published:24 April 2013

Using a garden experiment, we investigated some mechanisms responsible for spatial patterning in grasslands. We compared the spatial patterns of plant species differing in their clonal dispersal abilities and grown in several types of assemblages. Our results highlight that species spatial patterns not only depended on the clonal dispersal ability of species, but were also modified by the clonal dispersal ability of neighbours.

Free Access

Uncovering multiscale effects of aridity and biotic interactions on the functional structure of Mediterranean shrublands

  • Pages: 637-649
  • First Published:26 March 2013

Using a novel trait‐based and multiscale approach, we show that competition and facilitation jointly determine the functional structure of Mediterranean shrublands along a large aridity gradient. Competition mostly impacted on dominant plant species whereas facilitation affected subordinate and rare species. Overall, shift from competition to facilitation appears to be trait‐dependent along the aridity gradient.

Free Access

Changes in abiotic influences on seed plants and ferns during 18 years of primary succession on Puerto Rican landslides

  • Pages: 650-661
  • First Published:03 April 2013

Abiotic variables have important influences on plant succession on landslides and the relative influence of different abiotic variables changes with time. Improved predictability of temporal dynamics will rely not only on understanding the effects of initial disturbances and subsequent biological responses but also on the different and changing influences exerted by each abiotic variable.

Free Access

Do plant traits retrieved from a database accurately predict on‐site measurements?

  • Pages: 662-670
  • First Published:24 April 2013

This study reveals that the accuracy of traits retrieved from a database depends on the level of aggregation (lower at community level), the trait (lower in plastic traits) and the habitat type (lower in extreme habitats). For studies focussing on processes mainly acting at the site scale (e.g. trait‐environment relationships) traits retrieved from a regional database and filtered according to habitat will probably lead to good results. Whereas studying processes acting at the plot scale (e.g. niche partitioning), requires the additional effort of measuring traits on‐site.

Plant–herbivore interactions

Free Access

Caribou exclusion during a population low increases deciduous and evergreen shrub species biomass and nitrogen pools in low Arctic tundra

  • Pages: 671-683
  • First Published:24 April 2013

Caribou exclusion during a population low resulted in ecologically significant changes in the distribution of plant above‐ground biomass and nitrogen, further increasing the dominance of the three most abundant shrubs. These findings demonstrate that, despite uncertainty in herd recovery, Rangifer browsing impacts to both deciduous and evergreen shrub species should be considered for more robust projections of Arctic vegetation change.

Free Access

Let the best one stay: screening of ant defenders by Acacia host plants functions independently of partner choice or host sanctions

  • Pages: 684-688
  • First Published:24 April 2013

Defensive ant–plant mutualisms are challenged by non‐defending exploiter ants. However, the hosts can favour the persistence of defending mutualists by nourishing them with high amounts of extrafloral nectar, thereby enhancing their energy supply and thus their competitive capacities. Mutualisms remain stable when partner screening is based on traits of direct relevance for the mutualistic interaction.

Free Access

The impact of secondary compounds and functional characteristics on lichen palatability and decomposition

  • Pages: 689-700
  • First Published:06 March 2013

We have shown that lichen carbon‐based secondary compounds (CBSCs) regulate key processes such as lichenivory and decomposition, that lichen decomposability but not palatability are related to traits, and that these two processes are unrelated across species. These results highlight the potential role of lichen species differences in influencing ecosystem processes relating to decomposition and nutrient cycling and the role that grazers may play in driving this.

Habitat fragmentation

Free Access

Specialist species of wood‐inhabiting fungi struggle while generalists thrive in fragmented boreal forests

  • Pages: 701-712
  • First Published:24 April 2013

We show that the expected number of red‐listed species per a fixed amount of similar resources (dead trees) can be even more than 10 times higher in well‐connected than in fragmented surroundings, and thus protecting high‐quality areas that are well connected is conservationally more effective than protecting small fragments distributed across the landscape.

Free Access

Forest edges show contrasting effects on an austral mistletoe due to differences in pollination and seed dispersal

  • Pages: 713-721
  • First Published:24 April 2013

The alteration and transformation of the areas surrounding native forests due to anthropogenic disturbance can lead to ‘edge effects’. Our study shows clearly how secondary and tertiary responses to forest edges acted in opposite directions (increasing or decreasing plant reproductive performance), highlighting the need to study several successive processes that impact upon plant fitness under disturbance.

Plant population and community dynamics

Free Access

Trait‐mediated effects of environmental filtering on tree community dynamics

  • Pages: 722-733
  • First Published:12 March 2013

Individual performance is a function of an individual's traits and its environment. This function, known as an environmental filter, varies in space and affects community composition. We characterized trait‐mediated environmental filters that underlie spatial niche differentiation and life history trade‐offs for individuals in a tree community. The trait axes with the strongest filtering (a & c) and greatest variation in filters are shown (b & d).

Free Access

Evidence for transient dynamics in plant populations based on long‐term demographic data

  • Pages: 734-742
  • First Published:24 April 2013

Methods based on largest possible responses tend to overemphasize the role of transient dynamics. These results suggest that traditional, asymptotic analyses may be appropriate in many cases. Measures of transient potential can be helpful for identifying species and situations that may be prone to larger transient responses, but do not necessarily indicate that transient dynamics are more important in those systems.

Free Access

Genetically based vertical transmission drives the frequency of the symbiosis between grasses and systemic fungal endophytes

  • Pages: 743-752
  • First Published:24 April 2013

Theoretically, two mechanisms might contribute to variation in hereditary symbiont frequency among host populations: the impact of symbioses on host fitness, and symbiont transmission to offspring. We studied both mechanisms using a grass‐endophyte symbiosis in a native grass. We showed that transmission: (i) drives symbiont frequency variation in host populations, (ii) is not directly linked to the impact of symbiosis on host fitness, and (iii) is genetically based at population level.

Free Access

Variability in functional traits mediates plant interactions along stress gradients

  • Pages: 753-762
  • First Published:24 April 2013

This study demonstrates the generally overlooked importance of a nurse plant's vigor and morphology for its facilitative effects. Functional traits of the cushion plant Arenaria tetraquetra ssp. amabilis varied distinctively along two opposing stress gradients, in parallel to the magnitude of differences in micro‐environmental conditions between cushions and the surrounding open area, and also to the facilitation effect of cushions.

Plant–climate interactions

Free Access

Subordinate plant species enhance community resistance against drought in semi‐natural grasslands

  • Pages: 763-773
  • First Published:24 April 2013

While many experiments have been carried out to determine the effects of plant diversity on plant community insurance to drought, the results are still contradictory. Here, we demonstrated that, independent of plant diversity, the presence of drought‐resistant subordinate species increases plant community insurance against drought and hence is important for the functioning of grassland ecosystems.

Free Access

Inferring local processes from macro‐scale phenological pattern: a comparison of two methods

  • Pages: 774-783
  • First Published:24 April 2013

Time‐window and growing degree‐day methods provide remarkably congruent insights into the processes underpinning geographic variation in Q. robur first leafing dates. We find that a spatially invariant plastic response to temperature dominates spatiotemporal phenological variation, which means that it may be reasonable to substitute space for time to project how this species will respond to climate change. This study demonstrates the contribution that top‐down macroecological approaches can make to our understanding of large‐scale phenological processes.

Free Access

Latitudinal gradients as natural laboratories to infer species' responses to temperature

  • Pages: 784-795
  • First Published:25 February 2013

Macroclimatic variation along latitudinal gradients provides an excellent opportunity to investigate the role of temperature and the potential impacts of climate warming on terrestrial organisms. We review the use of latitudinal gradients for ecological climate‐change research, in comparison with altitudinal gradients and experimental warming, and illustrate their use and caveats with a meta‐analysis of latitudinal intraspecific variation in life‐history traits of plants.

Free Access

Local adaptation and plasticity of Erysimum capitatum to altitude: its implications for responses to climate change

  • Pages: 796-805
  • First Published:06 March 2013

As an effort to predict how alpine plant species may respond to climate change, we examined local adaptation and plasticity to altitude using Erysimum capitatum—a mustard that occurs in a broad altitudinal range. The results imply that alpine E. capitatum would suffer reduced seedling recruitment and higher mortality as a direct response to altered environment and possibly as a result of past adaptation to high altitude. In addition, environmental tracking by low‐altitude populations is predicted to have a limited role in maintaining future populations.

Plant–soil (below‐ground) interactions

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Competitive interactions across a soil fertility gradient in a multispecies forest

  • Pages: 806-818
  • First Published:07 March 2013

Whether plant competition grows stronger or weaker across a soil fertility gradient is an area of great debate in plant ecology. The intensity of competition among trees across a fertility gradient in a multi‐species forest was species‐ and context‐specific and more complicated than predicted by any one of the dominant existing theories in plant ecology.

Free Access

Preferences or plasticity in nitrogen acquisition by understorey palms in a tropical montane forest

  • Pages: 819-825
  • First Published:04 March 2013

We found that patterns in the distribution of understorey palms were related to nitrogen (N) uptake rates rather than preferences for N chemical forms. Down‐regulation of N uptake rates may be an important adaptation for plant species associated with low N soils, with plasticity in N acquisition patterns from various N sources important in alleviating competition for soil N.

Reproductive ecology

Free Access

Convergent specialization – the sharing of pollinators by sympatric genera of sexually deceptive orchids

  • Pages: 826-835
  • First Published:24 April 2013

Synthesis. This case of pollinator sharing confirms that morphological traits do not place a strong constraint on the evolution of sexual deception. However, interspecific differences in floral traits have important consequences for converting attraction into pollination, suggesting that selection can act to increase efficiency at multiple steps of the pollination process. This system provides a novel opportunity to elucidate the chemical, visual and morphological adaptations underpinning the evolution of sexual mimicry.

Erratum

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Erratum

  • Pages: 836
  • First Published:05 February 2013

Corrigendum

Free Access

Corrigendum

  • Pages: 836
  • First Published:02 November 2012