Macroclimate and Topography Interact to Influence the Abundance of Divaricate Plants in New Zealand

Lusk, Christopher H.; Wiser, Susan K.; Laughlin, Daniel C.

doi:10.3389/fpls.2020.00507

Cited by 6 publications

(3 citation statements)

References 46 publications

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“…Therefore, temperature is the most important factor that affects the yield and metabolic activities of the plants' community [49,50]. Moreover, there are interactions between topographical and climatic factors that influence the distribution of plants [51]. Our results showed that J. seravschanica had the lowest distribution in high slope and southern aspects.…”

Section: Discussionmentioning

confidence: 69%

Distribution and Physiology of Juniperus seravschanica Trees in the Genow—The Southernmost and Arid Habitat of Iran

Boogar

Sher

Seyedabadi

2022

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Juniperus seravschanica is the southernmost population of Juniperus that has a limited habitat in the world near the equator. In Iran, the lone habitat of this species in the Genow mountains has been endangered with thin foliage, abscissing needles, and dried shoots. The current study investigated the effects of climatic, genetic factors, and physiologic indices on the distribution of J. seravschanica. Distribution was evaluated for 450 ha and physiological indices were evaluated for two groups: (A) trees with dried branches and (B) trees without dried branches. Results showed that the distribution of J. seravschanica in the Genow habitat was influenced by elevation, slope degree, aspect, and distance to stream. Results also indicated that max temperature and precipitation are two effective factors that have the highest effects on falling needles and drying branches of J. seravschanica. Chlorophyll, relative water content (RWC), and relative turgidity (RT) are significantly influenced by max temperature. Endangered trees with dried branches had a lower chlorophyll content, RWC, and RT than trees without dried branches. Vulnerability of J. seravschanica was significantly influenced by its genetic structure. Results of AMOVA showed 83% genetic variability between two groups of J. seravschanica trees.

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Section: Discussionmentioning

confidence: 69%

Distribution and Physiology of Juniperus seravschanica Trees in the Genow—The Southernmost and Arid Habitat of Iran

Boogar

Sher

Seyedabadi

2022

Water

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“…Although our hypothesis involves soil fertility, our experiment did not test the effect of soil nutrients as it has previously been shown that divaricates are most prominent on fertile soils (Clarkson & Clarkson, 1994;Lusk et al, 2020a). Our experiment therefore TA B L E 6 Mortality (%) of broadleaved and divaricate seedlings apparently due to browsing, on unfenced plots in six New Zealand forests.…”

Section: Discussionmentioning

confidence: 98%

Climate influences the value of a plant structural defence against browsing

2020

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1. The circumstances that select for plant anti-herbivore defences are not well understood. In New Zealand, the 'divaricate' cage-like architecture of many woody plants may have arisen as a defence against avian browsing; it also has some ability to deter browsing by introduced deer. Its prominence on alluvial soils in frosty and droughty areas led us to hypothesize that structural defences are of most value where fertile soils coincide with climatic constraints that prevent plants from quickly growing out of the browse zone. 2. We tested this hypothesis by growing seedlings of three divaricate species and their broadleaved congeners on fenced and unfenced plots beneath tree-fall gaps at three humid frost-free sites in the North Island of New Zealand, and at three colder and drier sites in the South Island. Soil total phosphorus levels were moderate to high at all sites (344-961 ppm), and pellet counts indicated similar average deer densities at North and South Island sites, enabling us to attribute variation in seedling growth and survival primarily to climatic differences between our sites. 3. On fenced plots, average relative height growth rates in the North Island exceeded those on the southern sites by 64%, and growth of broadleaved species averaged 132% and 99% greater than that of divaricate congeners at North and South Island sites, respectively. On the northern sites, broadleaved species also held a large (137%) net height growth advantage over divaricates even on unfenced plots. In contrast, exposure to browsing on the coldest sites resulted in complete loss of the broadleaved net height growth advantage. 4. Synthesis. Even in the presence of deer, divaricate plants were overgrown on humid frost-free sites, but not on colder and drier sites, where browsing neutralized the superior growth potential of broadleaved species. The cost of structural defences therefore paid off only on sites where climatic adversity reduces the ability of plants lacking such defences to grow quickly out of the browse zone, in agreement with our hypothesis.

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“…As well as reconciling the two competing explanations of the divaricate habit in New Zealand, this study therefore adds to evidence that climate modulates the adaptive value of structural defences against browsing, worldwide. The especially high incidence of spinescence in fertile savannas (Scholes, 1990 ), and of cage architectures on alluvial soils in New Zealand (Lusk et al ., 2020 ), suggest that a selection for structural defences is strongest when high nutrient availability coincides with strong climatic constraints on plant growth rates (Lusk et al ., 2016 ).…”

Section: Discussionmentioning

confidence: 99%

A dated phylogeny shows Plio‐Pleistocene climates spurred evolution of antibrowsing defences in the New Zealand flora

2021

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Some plant traits may be legacies of coevolution with extinct megafauna. One example is the convergent evolution of 'divaricate' cage architectures in many New Zealand lineages, interpreted as a response to recently extinct flightless avian browsers whose ancestors arrived during the Paleogene period. Although experiments have confirmed that divaricate habit deters extant browsers, its abundance on frosty, droughty sites appears consistent with an earlier interpretation as a response to cold, dry Plio-Pleistocene climates.We used 45 protein-coding sequences from plastid genomes to reconstruct the evolutionary history of the divaricate habit in extant New Zealand lineages. Our dated phylogeny of 215 species included 91% of New Zealand eudicot divaricate species.We show that 86% of extant divaricate plants diverged from non-divaricate sisters within the last 5 Ma, implicating Plio-Pleistocene climates in the proliferation of cage architectures in New Zealand.Our results, combined with other recent findings, are consistent with the synthetic hypothesis that the browser-deterrent effect of cage architectures was strongly selected only when Plio-Pleistocene climatic constraints prevented woody plants from growing quickly out of reach of browsers. This is consistent with the abundance of cage architectures in other regions where plant growth is restricted by aridity or short frost-free periods.

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Macroclimate and Topography Interact to Influence the Abundance of Divaricate Plants in New Zealand

Cited by 6 publications

References 46 publications

Distribution and Physiology of Juniperus seravschanica Trees in the Genow—The Southernmost and Arid Habitat of Iran

Distribution and Physiology of Juniperus seravschanica Trees in the Genow—The Southernmost and Arid Habitat of Iran

Climate influences the value of a plant structural defence against browsing

A dated phylogeny shows Plio‐Pleistocene climates spurred evolution of antibrowsing defences in the New Zealand flora

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