Special Features | YouFeelGreen

Michael Foisy and colleagues contributed a paper to our latest special feature: Macroevolutionary perspectives on biotic interactions. Find out more about their paper below.

A brief history of the project

When an insect chomps on a plant, sometimes the plant tissue will release latex or resin – a “goo” that can be toxic, difficult to digest, and a real nuisance for insect mouthparts. Latex and resin are stored in pressurized canals, which, when damaged, rupture and spill their contents out in dramatic fashion (Figure 1). These canal systems have evolved many times across plants, and play an important role in defence against herbivorous insects.

Rich latex exuded by Papaver somniferum (Papaveraceae), near Chihuahua, Mexico (Photo: Anurag Agrawal).

In 1991, Farrell et al. conducted a now classic study testing whether plants with these pressurized canals are more diverse than closely related plants without canals. Their results were striking: 13 of the 16 comparisons revealed higher species richness when canals were present, supporting the prediction that plant defensive traits are associated with higher diversification rates (i.e. the accumulation of species over time, estimated as the net of speciation minus extinction) in plants.

Their study was one of the first to show strong support for a classic hypothesis about how coevolution between plants and insects could generate biological diversity (Ehrlich & Raven, 1964), and their work remains a prominently cited empirical example even today.

Retesting Farrell et al. 1991

In the three decades since the original study by Farrell et al. (1991), major changes to plant systematic relationships have occurred, and we now have phylogenetic comparative methods that go beyond the sign test they used. In particular, we can explicitly model trait evolution and/or diversification rates. Therefore, our goal was to reassess Farrell’s classic test of whether these defensive “goos” are associated with increased species diversity, but to do so using modern methods and data.

We collected data on the occurrence of latex and resin canals in approximately 300 families and 1000 genera of plants, and used these data (along with updated phylogenetic hypotheses for plant relationships) to test the association between canal evolution and lineage diversification rates. We tested this hypothesis at multiple scales: (i) between clades and (ii) within clades.

As usual, biology is complicated

When we updated and added to the Farrell dataset, interestingly, we no longer found strong support for a relationship between canal evolution and lineage diversification. This was surprising, and so we wanted to zoom in on some of these comparisons, to look at the tempo of diversification in relation to trait evolution.

Within clades, we had enough data to look at two groups: Papaveraceae (poppies) and Araceae (arums). In poppies, the timing of latex evolution coincided with a burst of diversification; however, in Araceae, canal evolution appears to be entirely out of tempo with diversification.

Figure 2 (Read the full paper: https://doi.org/10.1111/1365-2745.13203)

Figure 2 is a simplified version of the figure from our paper. Canal origins are indicated by stars (yellow = latex, green = resin), while shifts in diversification rate are indicated by circles (red = increase, blue = decrease). The relative rates of diversification are shaded in grayscale (darker = higher rates). These data show that diversification coincides with latex evolution in poppies (left), but is uncoordinated with latex and resin evolution in arums (right).

Looking forwards

Thus, it seems that latex and resin canals may not be as consistently replicable drivers of lineage diversification across plants as we previously thought. Future studies could follow up on this work as more data becomes available, for example using more sophisticated models of trait dependent diversification, or taking other factors (such as clade age) into account. We are looking forward to the day that more data are available, so that this association can be even more rigorously examined in even more clades. But in the meantime, latex and resin remain super cool defensive traits with large consequences for plant fitness. Who doesn’t want a powerful goo weapon to fight their enemies?!

Michael Foisy, Loren Albert, Daniel Hughes & Marjorie Weber.

Read the full paper online: Do latex and resin canals spur plant diversification? Re-examining a classic example of escape and radiate coevolution

Share this:

PrintEmailTweet

Like this:

LikeLoading…

First published on 2019-07-01 13:25:53

Original Source

Cynthia Chang and Ben Turner are the guest editors for our latest special feature: Ecological Succession in a Changing World. Cynthia and Ben tell us more about their special feature and the inspiration behind it, below.

There is no doubt that succession is a foundation of ecology. However, when ecologists talk about succession, it often seems to be in a historical context. This has caused some to ask, “Is succession passé?” The goal of our special feature is to answer with a resounding “No!” and place succession research in a contemporary context, highlighting its relevance in modern ecological theory and pressing applied issues such as global change and restoration research.

This motivated us to organize a symposium at the Ecological Society of America conference in August 2017, to highlight how studying succession brings new insights into community assembly theory, plant-belowground interactions, and restoration and global change research.

This Journal of Ecology special feature is an expanded result of these efforts. The collection of papers represent a flavor of all the different kinds of contemporary work currently being done on succession. They represent a range of biomes and ecosystems, including everything from tropical forests, volcanic landscapes, glacier retreats, grasslands, and old-fields.

This special feature presents 11 articles and an editorial that encompass 4 main themes:

1. Generalizations about succession: Prach & Walker, Chang et al., Fischer et al., and Clark et al. provide novel conclusions regarding post-disturbance successional trajectories.

2. Influence of dispersal limitation and habitat size on succession: Makoto & Wilson, van Breugel et al., and Liu et al. show how succession research can be applied to understanding restoration efforts, the effects of habitat fragmentation, as well as community response to global climate change.

3. Functional trait dynamics over the course of succession: Duffin et al. show how functional trait change over the course of succession can help ecologists understand community dynamics during ecosystem development.

4. Influence of belowground community interactions on succession: Recent advances in metagenomics allow us to better understand linkages between plant and belowground community feedbacks over the course of succession. Turner et al., Koziol & Bever, and Teste & Laliberté showcase new insights into the important role of belowground communities.

Read the special feature editorial: https://doi.org/10.1111/1365-2745.13132

Overall, these studies highlight the relevance of succession to modern ecological theory and novel ways for succession research to be applied to important societal issues in a rapidly changing world. Our hope is that this special issue not only highlights the continued value and relevance of successional research, but also encourages future research to be better integrated into relevant global change issues.

Cynthia Chang (University of Washington, Bothell, USA) and Ben Turner (Smithsonian Tropical Research Institute, Panama)

Read the latest issue of Journal of Ecology online, including Cynthia and Ben’s special feature: Ecological Succession in a Changing World.