No evidence for extrafloral nectaries in Erythranthe angulosa
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Abstract
Extrafloral nectaries (EFNs) are a widespread plant defense mutualism trait and are highly convergent, appearing in hundreds of plant lineages worldwide. Here we investigate a report of possible EFNs in Erythranthe angulosa , a recently-described California wildflower. We integrate field observations, insect bioassays, an induction experiment, and microscopy to test for signatures of EFN function, finding no evidence that the distinctive axillary swellings produced by E. angulosa function as EFNs. We also uncovered two distinct morphs at the type locality of E. angulosa that diverge in the number of axillary swellings produced, as well as other shoot architecture traits such as stem thickness, leaf size, and branch number. Although the axillary swellings appear to not function as EFNs, they remain a compelling morphological variant within the yellow monkeyflowers that may perform storage or another unknown function.
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Test for Genetic and Environmental Variation
Thanks for putting this out, it's a nice clean write-up and I appreciated that the data and code are on GitHub. I pulled the induction file and replotted the counts with treatment on the x axis within each morph. The null looks well supported in the thin-stemmed morph, where you have 15 to 17 plants per treatment and JA and clipping both come out slightly below control if anything.
The robust morph is where I got curious, since that's the one actually producing swellings in quantity (around 10 to 12 versus 1 to 2) but it has 19 plants total against 65 for the thin-stemmed morph, so 4 to 6 per treatment. All three treatments sit a bit above control there, though the control values themselves run from 8 to 16, so I don't think it means much. With that few plants I'd guess only a fairly large …
Test for Genetic and Environmental Variation
Thanks for putting this out, it's a nice clean write-up and I appreciated that the data and code are on GitHub. I pulled the induction file and replotted the counts with treatment on the x axis within each morph. The null looks well supported in the thin-stemmed morph, where you have 15 to 17 plants per treatment and JA and clipping both come out slightly below control if anything.
The robust morph is where I got curious, since that's the one actually producing swellings in quantity (around 10 to 12 versus 1 to 2) but it has 19 plants total against 65 for the thin-stemmed morph, so 4 to 6 per treatment. All three treatments sit a bit above control there, though the control values themselves run from 8 to 16, so I don't think it means much. With that few plants I'd guess only a fairly large effect would be detectable, which is a bit different from no induction occurring. Might be worth stating the per-morph n and flagging it, since the two morphs currently get read together. It'd also help to dodge or facet Figure 2 by treatment, since the boxes pool all four treatments within each morph and the comparison is hard to see.
One other question: was there anything confirming the JA actually took effect in these plants? Trichome density might be a cheap internal check given it's JA-responsive in this clade and you noticed morph differences in trichomes anyway.
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