Archivos de diario de junio 2023

10 de junio de 2023

Splitting of Lysimachia arvensis colour morphs

Lysimachia is a fairly large genus (few hundred species), but is relatively poorly represented in Australia, with a small handful of naturalised non-native species, and a small handful of native species (although only one, L. japonica, is widely distributed in Australia, with others such as L. fortunei or L. vulgaris var. davurica known from one or very few locations, and are possibly here via waterbird dispersal from outside Australia). One species, L. arvensis, is by far the most widely distributed in Australia and certainly the most well-known as a common weed in disturbed sites such as pastures, wasteland, weedy creeklines, etc. It's found in all Australian states and territories except the NT. Perhaps its most salient feature is the presence of two different flower colour morphs: a bright orange form and a rich blue form.

Many sources, including (until recently) Plants of the World Online - the taxonomic authority we try to adhere to for plants on iNat - give these two forms official varietal names, i.e., Lysimachia arvensis var. arvensis for the orange form, and Lysimachia arvensis var. caerulea for the blue form. Although Australia's state herbaria don't formally recognise these two variety names, they do recognise the presence of both colour morphs in Australia.

Interestingly, and perhaps one of the reasons why the two morphs have been treated as the same species for so long, is that they are not only sympatric, but in many cases directly co-occur. A perfect example is this observation just uploaded today by @russellcumming:

However, as some of you may have noticed, Lysimachia arvensis var. caerulea is no longer on iNat as of this morning; it has been elevated to full species, and is now L. loeflingii.

This change was based on this 2022 paper: It has also now been reflected in POWO (hence the change now in iNat).

Some relevant parts of the paper:

"Lysimachia arvensis (L.) Manns & Anderb. (synonym: Anagallis arvensis L.) and L. monelli (L.) Manns & Anderb. (synonym: Anagallis monelli L.) are two Mediterranean species that show intraspecific flower colour polymorphism (Ferguson, 1972; Pujadas, 1997). Petal colours are genetically determined (Freyre & Griesbach, 2004; Sánchez-Cabrera et al., 2021), and in both species blue- and red-flowered individuals are found due to the presence of different anthocyanins in their petals (Ishikura, 1981; Quintana et al., 2008; Sánchez-Cabrera et al., 2021). The species differ in ploidy, L. arvensis being tetraploid (revised by Pastor, 1992) and L. monelli being diploid (Kress, 1969; García Pérez et al., 1997).

...Blue- and red-flowered plants may appear in sympatric and allopatric populations, and pollinators show a preference for visiting blue-flowered plants in Mediterranean polymorphic populations (Ortiz et al., 2015) and high colour constancy patterns (Jiménez-López et al., 2020a). Hand-pollination between red and blue individuals gives rise to homogeneous F1 progeny with salmon-coloured flowers (Jiménez-López et al., 2020a), but these are infrequent in wild populations (Jiménez-López et al., 2020c). This ‘hybrid’ phenotype has been described as Anagallis × amoena Heldr. ex Halácsy (de Halácsy, 1904: 11). Nuclear microsatellite markers reconstructed two independent genetic groups for each colour morph, supporting this reproductive isolation between them (Jiménez-López et al., 2020b). All this ecological, morphological, reproductive and molecular evidence suggests that the two colour morphs of L. arvensis are independent lineages.

...Previous phylogenetic studies have scarcely explored the potential implications of corolla colour polymorphism in taxon delimitation in L. arvensis and L. monelli because this trait was considered part of the infraspecific variation. Consequently, only one colour morph per species was sampled in most of the molecular analyses (Martins, Oberprieler & Hellwig., 2003; Manns & Anderberg, 2005, 2007a; Anderberg, Manns & Källersjö., 2007; Yan et al., 2018).

...Lysimachia arvensis is a Mediterranean species currently distributed across the world as an alien species. It is annual, self-compatible (Gibbs & Talavera, 2001) and tetraploid (2x = 40; revised by Pastor, 1992).

...Our phylogenetic results based on nuclear ITS regions indicate that blue- and red-flowered individuals of L. arvensis and L. monelli are independent taxa (Fig. 2), reinforcing ecological, morphological and reproductive evidence.

...Although the presence of different ITS sequences in the red- and blue-flowered individuals of L. arvensis collected from the same populations had already been reported by Manns & Anderberg (2007b), the strong support of our ITS (100 BS, 0.999 PPS) and the species delimitation results (Table 4, Fig. 5) indicate that the two colour morphs of L. arvensis are different lineages and belong to different taxa. The ITS phylogenetic reconstruction is also congruent with recent studies on L. arvensis in which red- and blue-flowered plants were separated in different clades with nuclear microsatellite markers (Jiménez-López et al., 2020b).

...Flower colour constitutes a pivotal evolutionary force to speciation in several groups of plants (Carlson & Holsinger, 2015; Ellis & Field, 2016; Takahashi, Takakura & Kawata, 2016; Narbona et al., 2018), and it has been proposed as a ‘magic trait’, that is a trait ‘encoded by genes subjected to divergent selection that affect pleiotropically reproductive isolation’ (Servedio et al., 2011). However, according to ancestral state reconstruction, flower colour does not seem the trait promoting divergence between lineages of L. arvensis, although it does in L. monelli with posterior polyploidization events (see below). Ancestral state reconstruction of this trait invoked a blue-flowered common ancestor for this Mediterranean Lysimachia, and the transition to red-flowered plants probably occurred only once for the red-flowered common ancestor of red L. arvensis and red L. monelli. This kind of transition from blue to red flowers is quite frequent due to inactivation of a branch of the anthocyanin pathway (Rausher, 2008), and it has been found in L. arvensis lineages (Sánchez-Cabrera et al., 2021). In other plant groups, red-flowered species are usually derived from blue-flowered species (Kay et al., 2005; Wilson et al., 2007; Rausher, 2008; Wessinger & Rausher, 2012). In our study, the blue ancestor probably gave rise to two lineages, one entirely blue (which includes the blue lineage of L. arvensis) and another that subsequently separated into blue- and a red-flowered subclades (the latter including the red lineage of L. arvensis and L. monelli).

...Our results have taxonomic implications for the colour lineages of L. arvensis and L. monelli as each lineage should be defined as different taxa supported by morphological, phylogenetic and geographical data.

...Red-flowered plants of Lysimachia arvensis should maintain this name because Linnaeus in 1753 described the species from red-flowered plants.

...Blue plants of L. arvensis should be called with the specific epithet latifolia as it was the first name employed by Linnaeus in 1753 for plants with blue flowers. However, the epithet latifolia already exists in Lysimachia for a different taxon [Lysimachia latifolia (Hook.) Cholewa in Phytoneuron 28: 1–2 (2014) = Trientalis latifolia Hook., Fl. Bor. Amer. 2(9): 121 (1839), a plant described from Washington]. Therefore, we have selected the name L. loeflingii because Linnaeus in 1753 described blue-flowered plants from materials collected by Loefling in Spain."

So what all this means is that, anything we have been identifying as L. arvensis var. caerulea in Australia is now directly referrable to L. loeflingii. For iNat observations that were already ID'ed to this variety, no further work is needed, as the taxon swap moved them over automatically to the new species. However, in many cases, blue-flowered observations have been ID'ed only to species (which was fine and correct under the old scheme), so these are now incorrectly ID'ed. Similarly, observations that had one ID of L. arvensis and one ID of the blue variety will now have been bumped back to genus due to the now conflicting IDs. I'm going to go through today and correct IDs where I can.

There is one final important thing from the paper, which is the key they provide:

1 . Perennial plants, rarely annual herbs with a single stem; stem nodes with (two) three or four (five) verticillated leaves; fertile nodes with a single flower in the axil of each leaf; flowers with the corolla (14) 16–25 mm in diameter, styles 3–4 mm in length 2

  • Annual plants; nodes generally with opposite leaves, rarely with three verticillated leaves; fertile nodes with two flowers, one in each leaf axil, rarely with a single flower; flowers with corolla 3–12 (14) mm in diameter; styles 1.0–2.5 mm in length 3

2 . Flowers with orange or red corolla Lysimachia collina

  • Flowers with blue corolla Lysimachia monelli

3 . Plants generally compact; internodes generally shorter than the leaves; leaves, at least the upper ones, erect-patent, lanceolate or elliptic-lanceolate, acute; fruit pedicels generally shorter than internodes; flowers with blue corolla, with elliptical lobes, strongly serrated in the upper half of the margin, covered with hairs with (three) four (five) cells, the terminal elliptical or sub-cylindrical, about the size and shape of the adjacent cell, sometimes glabrous Lysimachia foemina

  • Plants generally graceful; internodes often longer than leaves; leaves patent, ovate or ovate-lanceolate, obtuse or subacute; fruit pedicels generally larger than internodes; flowers with blue or orange-red corolla, with lobes broadly ovate, denticulate, with the margin densely covered with hairs with three cells, the terminal globose, larger than the underlying cell 4

4 . Flowers blue 5

  • Flowers orange or red Lysimachia arvensis

5 . Small plants, generally < 10 cm in length; root neck generally covered by secondary roots; ovate leaves; flowers with blue or pale blue corolla, often surpassed by calyx; styles 1.0–1.5 mm in length; Lysimachia talaverae

  • Generally large plants, up to 60 cm in length; bare root neck without secondary roots; ovate-lanceolate leaves, at least in the upper half of the stem; blue corolla, usually longer than the calyx; styles 2.0–2.5 mm in length Lysimachia loeflingii

What is immediately noticeable here is that, when separating L. arvensis and L. loeflingii, the only differentiating character provided in the key is flower colour! This has important implications because many observations in iNat are of non-flowering plants. I'm unsure what to do with all of these; reID them to genus, or leave them as L. arvensis for now? (in my personal experience at least, arvensis is far more common, at the very least in Sydney, compared to loeflingii, so on balance of probability a lot of non-flowering observations are probably of arvensis, but of course this is not a compelling argument)

The start of the paper does mention there are other differences between the orange and blue, namely:
"...colour morphs also differ in other traits such as flowering phenology or type of herkogamy (Arista et al., 2013; Jiménez-López et al., 2020c)". They also note that "The colour morphs show different geographical distributional patterns, blue-flowered plants appearing mainly in drier Mediterranean localities and red-flowered plants being predominant in more temperate areas (Arista et al., 2013)." However, given the co-occurrence of both species in Australia in the same populations (also noted in the paper: "Blue- and red-flowered plants may appear in sympatric and allopatric populations"), this geographical aspect doesn't seem like a helpful separator.

The Arista et al. paper found differences in flowering time in Mediterranean populations. A small selection of text from that paper:

"We found significant negative associations between blue morph frequency and latitude of populations, and between similarity in blue morph frequency and geographical distance of population pairs. This means that a geographical pattern of flower colour exists in L. arvensis, and it seems to be related to climatic features, which suggests that flower colour is not a neutral trait (Mayr 1965). The correlations found between blue morph frequency and the environmental variables studied indicate that blue plants are more frequent in dryer, hotter Mediterranean localities while red plants predominate in more temperate Oceanic areas. This could reflect a differential adequacy of morphs to environmental conditions that is also supported by the fact that red plants in southern mixed populations frequently occupied the wettest or shadiest places (M. Arista & P. L. Ortiz).

...In our experimental study, germination, seedling mass, seedling survival, and flower and ovule production all showed different morph-by-environment interactions. The blue morph showed lower germination in the shade and higher seedling mass in the sun treatment, while the red morph showed lower survival in the dry–sun combination, more flowers in the sun–wet combination and more ovules at sun or wet treatments. Since some treatment effects on the components of plant performance may counteract each other, they are poor predictors of the overall effect when analysed separately. Only by considering overall fitness, instead of each trait separately, enables us to assess how each colour morph is affected by the treatments (García & Ehrlen 2002). Overall male and female fitness of blue morph was markedly higher in dry conditions, and this suggests a better tolerance to more xeric environments. However, our experimental study failed to find a clear pattern of adequacy of red morph to more mesic environments as only in wet-sun but not in wet-shade conditions was overall female fitness higher (male fitness was also higher but not significantly). In fact, the wet–shade combination seems to be the less favourable for L. arvensis as both morphs showed their lowest fitness. Thus, the Mediterranean environment seems to be more suitable for the blue morph, while the red morph seems to perform better in wet and sunny places, such as those where it usually occurs in central Europe. But, it is possible that other environmental factors not considered here could also be responsible for the geographic pattern found in our survey.

...Although most of the traits studied were affected by the experimental treatments, onset of flowering was markedly earlier in the blue morph in relation to the red morph without any morph-by-environment interactions. This difference between morphs, regardless of growing conditions, is one of our most notable results and suggests that this trait is linked to flower colour and is genetically determined. This pattern of flowering can be also observed in natural mixed populations (pers. obs.)

...Taking into account all our results, we found in L. arvensis many monomorphic populations that were spatially isolated, and some mixed populations with observational and experimental evidence of divergence in flowering times between morphs. It is obvious that long-term spatial segregation can generate reproductive isolation and trigger speciation (Mayr 1965; Coyne 1992; Doebeli & Dieckmann 2003). However, even in absence of spatial barriers, differences in flowering time between morphs could cause assortative mating, leading to a decrease in gene flow between them and eventually to allochronic speciation (Fox 2003; Weis et al. 2005; Savolainen et al. 2006; Gavrilets & Vose 2007).

...The marked difference in flowering time between colour morphs leaves open the potential for assortative mating and speciation in L. arvensis"

So maybe these differences could help differentiate in Australia, but I am unsure.

The herkogamy difference (anther–stigma separation) relevant to the Jiménez-López et al. citation above, is unhelpful here as it's a flowering trait.

For now, I'm not going to touch the existing non-flowering observations and leave them IDed as L. arvensis, even though at very least a small subset of them will almost certainly be L. loeflingii. For any non-flowering ones I upload from now on, however, I will only ID to genus. But any with flowers, I will go through now and add IDs where needed.

I will also note that, even if you don't accept this change (which of course is completely fine), L. arvensis var. caerulea is now a synonym on iNat, so it is best to use the new name L. loeflingii; they refer to the same thing on iNat. If things change again in the future, it will be much easier to change Australian observations back with minimal work.

Just for reference, here is the iNat swap:
and here is the original flag asking for the swap:

@nicklambert @possumpete @wcornwell @hsauquet @russellbarrett @russellcumming @alx4mtmel @scottwgavins @gregtasney @reiner @bushbandit @mattintas @mftasp @rfoster @ellurasanctuary @margl @terra_australis @jackiemiles @onetapir @gtaseski @aavankampen
Please tag anyone I've missed

Publicado el 10 de junio de 2023 por thebeachcomber thebeachcomber | 41 comentarios | Deja un comentario
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