Lejeunea is a largely epiphytic, subcosmopolitan liverwort genus with a complex taxonomic history. Species circumscriptions and their relationships are subject to controversy; biogeographic history ...and diversification through time are largely unknown.
We employed sequences of two chloroplast regions (trnL-trnF, rbcL) and the nuclear ribosomal ITS region of 332 accessions to explore the phylogeny of the Harpalejeunea-Lejeunea-Microlejeunea complex. Lejeunea forms a well-supported clade that splits into two main lineages corresponding to L. subg. Lejeunea and L. subg. Crossotolejeunea. Neotropical accessions dominate early diverging lineages of both main clades of Lejeunea. This pattern suggests an origin in the Neotropics followed by several colonizations from the Neotropics into the Paleotropics and vice versa. Most Afro-Madagascan clades are related to Asian clades. Several temperate Lejeunea radiations were detected. Eighty two of the 91 investigated Lejeunea species could be identified to species level. Of these 82 species, 54 were represented by multiple accessions (25 para- or polyphyletic, 29 monophyletic). Twenty nine of the 36 investigated species of L. subg. Lejeunea were monoicous and 7 dioicous. Within L. subg. Crossotolejeunea, 15 of the 46 investigated species were monoicous and 31 dioicous. Some dioicous as well as some monoicous species have disjunct ranges.
We present the first global phylogeny of Lejeunea and the first example of a Neotropical origin of a Pantropical liverwort genus. Furthermore, we provide evidence for the Neotropics as a cradle of Lejeunea lineages and detect post-colonization radiations in Asia, Australasia, Afro-Madagascar and Europe. Dioicy/monoicy shifts are likely non-randomly distributed. The presented phylogeny points to the need of integrative taxonomical studies to clarify many Lejeunea binomials. Most importantly, it provides a framework for future studies on the diversification of this lineage in space and time, especially in the context of sexual systems in Lejeuneaceae.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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•Species diversity within Australasian Plagiochilaceae is 29% higher than currently recognized.•36% of currently recognized Australasian species have circumscription ...issues.•Integrative taxonomy contributes to resolving robust species hypotheses within a challenging lineage of leafy liverwort.
As a framework for revisionary study of the leafy liverwort Plagiochila in Australia, two methods for species delimitation on molecular sequence data, General Mixed Yule Coalescence model (GMYC) and Automatic Barcode Gap Discovery (ABGD) were applied to a dataset including 265 individuals from Australia, New Zealand, and the Pacific. Groups returned by GMYC and ABGD were incongruent in some lineages, and ABGD tended to lump groups. This may reflect underlying heterogeneity in the history of diversification within different lineages of Plagiochila. GMYC from trees calculated using three different molecular clocks were compared, in some lineages different primary species hypotheses were returned by analyses of trees estimated under different clock models, suggesting clock model selection should be a routine component of phylogeny reconstruction for tree-based species delimitation methods, such as GMYC. Our results suggest that a minimum of 71 Plagiochilaceae species occur in Australasia, 16 more than currently accepted for the region, comprising 8 undetermined species and 8 synonyms requiring reinstatement. Despite modern taxonomic investigation over a four decade period, (1) real diversity is 29% higher than currently recognized; and (2) 12 of 33, or 36%, of currently accepted and previously untested Australasian species have circumscription issues, including polyphyly, paraphyly, internal phylogenetic structure, or combinations of two or more of these issues. These both reflect the many challenges associated with grouping decisions based solely on morphological data in morphologically simple yet polymorphic plant lineages. Our results highlight again the critical need for combined molecular-morphological datasets as a basis for resolving robust species hypotheses in species-rich bryophyte lineages.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Shifts in sexual systems are among the most common and important transitions in plants and are correlated with a suite of life-history traits. The evolution of sexual systems and their relationships ...to gametophyte size, sexual and asexual reproduction, and epiphytism are examined here in the liverwort genus Radula. The sequence of trait acquisition and the phylogenetic correlations between those traits was investigated using comparative methods. Shifts in sexual systems recurrently occurred from dioecy to monoecy within facultative epiphyte lineages. Production of specialized asexual gemmae was correlated to neither dioecy nor strict epiphytism. The significant correlations among life-history traits related to sexual systems and habitat conditions suggest the existence of evolutionary trade-offs. Obligate epiphytes do not produce gemmae more frequently than facultative epiphytes and disperse by whole gametophyte fragments, presumably to avoid the sensitive protonemal stage in a habitat prone to rapid changes in moisture availability. As dispersal ranges correlate with diaspore size, this reinforces the notion that epiphytes experience strong dispersal limitations. Our results thus provide the evolutionary complement to metapopulation, metacommunity and experimental studies demonstrating trade-offs between dispersal distance, establishment ability, and life-history strategy, which may be central to the evolution of reproductive strategies in bryophytes.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Australia is an excellent setting to explore relationships between climate change and diversification dynamics. Aridification since the Eocene has resulted in spectacular radiations within one or ...more Australian biomes. Acacia is the largest plant genus on the Australian continent, with around 1000 species, and is present in all biomes. We investigated the macroevolutionary dynamics of Acacia within climate space.
We analysed phylogenetic and climatic data for 503 Acacia species to estimate a time-calibrated phylogeny and central climatic tendencies for BioClim layers from 132 000 herbarium specimens. Diversification rate heterogeneity and rates of climate space exploration were tested.
We inferred two diversification rate increases, both associated with significantly higher rates of climate space exploration. Observed spikes in climate disparity within the Pleistocene correspond with onset of Pleistocene glacial–interglacial cycling.
Positive time dependency in environmental disparity applies in the basal grade of Acacia, though climate space exploration rates were lower. Incongruence between rates of climate space exploration and disparity suggests different Acacia lineages have experienced different macroevolutionary processes. The second diversification rate increase is associated with a south-east Australian mesic lineage, suggesting adaptations to progressively aridifying environments and ability to transition into mesic environments contributed to Acacia’s dominance across Australia.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Plagiochila is the most diverse genus of liverwort by number of described species, with 1600 validly published names. The typification and application of names within the context of such ...nomenclatural diversity is therefore critical. Typification statements made over five decades of revisionary study for 95 validly published species names, and two varieties, in Australasian Plagiochilaceae are reviewed with reference to the International Code of Nomenclature for algae, fungi, and plants (Code) and the citation of original material in the protologue, to establish for each the type specimens and their status. This review serves two purposes, firstly to confirm type specimen status given the recent suggestion that type citations by Bonner in Index Hepaticarum Volume 1 not be accepted as effective (if inadvertent) lectotypifications; and secondly to provide a data-based assessment of typification practice with reference to a relatively well-studied bryophyte group. None of the works reviewed were error-free with regards to typification practice. The most common errors were the citation of a holotype when none exists, and neglecting earlier type citation statements and their context. However, no instance where these errors impacted the application of names was found, implying authors are generally conscientious in their identification of original material. Three recommendations to improve typification practice are made: firstly, taxonomists need to utilise available online biodiversity resources to establish for themselves the original material and its context; secondly, greater scrutiny of type statements in existing primary and secondary literature is required; and thirdly, we need proactive education and self-education in the Code's requirements.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
Abstract
All studied leafy liverworts have shoots with leaf to underleaf ratios of either 2:1 or 1:1. These ratios are the product of growth by either helical or pendular segmentation of the ...tetrahedral apical cell. Here we report that Herzogianthus vaginatus has a leaf to underleaf ratio approaching 3:1 on primary shoots, and on secondary shoots the ratio is closer to 4:1. These ratios are incompatible with the simple helical or pendular growth patterns found in other leafy liverworts. Further, the sequence of leaves and underleaves on Herzogianthus shoots is not wholly regular, which is previously unrecorded. We assess potential growth models that may explain the leaf to underleaf ratios and architecture of Herzogianthus shoots, including (1) branch modification, (2) merophyte or leaf-initial duplication and (3) changes in segmentation sequences. We compared leaf sequences produced by pendular and helical segmentation and a range of non-standard models, with sequences observed on shoots of Herzogianthus. Structure allows us to discriminate between the many alternative growth models, because each make testable predictions about leaf and underleaf sequences. We propose that Herzogianthus possesses growth processes unique among leafy liverworts, in which the direction of helication periodically and, sometimes irregularly, reverses. This, in combination with the secondary shoots having different growth patterns from primary shoots, emphasizes that Herzogianthus warrants detailed histological study to test our proposition.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Cryptic bryophyte species exhibit a decoupling in the degree of morphological and molecular divergence, as a result of different processes, from recent divergence to stasis. Here a body of cryptic ...species literature comprising 110 papers published between 2000 and end 2018 is reviewed. Most studies of cryptic species focused on northern hemispheric taxa, but we do not yet have sufficient studies to assess whether a geographic bias in the distribution of cryptic species exists, and we don’t know how many cryptic bryophyte species there might be globally. Fully two-thirds of all studies on cryptic bryophyte species rested their claims of morphological crypsis on previous taxonomic investigations, without revision of morphology to confirm cryptic species status. There is more than one kind of morphological crypsis, and while quantification of morphological patterns can contribute to our understanding of crypsis this is a widely neglected component. The usage of ‘cryptic species’ as an etymological tool to flag instances where traditional species concepts are deficient devalues the term, and a distinction between genuine crypsis and business as usual revision of species circumscription should be re-established and maintained. Hybridisation is possibly an under-appreciated contributor to cryptic species, but inference of hybridization has been limited by study design. Opportunities exist in the application of geometric morphometric methods and next generation sequencing technologies to overcome intrinsic limitations in traditional morphological and molecular data sources.
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•Radula, a leafy liverwort genus, agglutinates a mixture of cosmopolitan and geographically restricted lineages.•Range size was phylogenetically constrained in Australasian and ...Neotropical subgenera.•Plate tectonics could have played a major role in Radula present distribution.•Niche conservatism seems to account for the restricted geographic ranges in the genus Radula.
Why some species exhibit larger geographical ranges than others, and to what extent does variation in range size affect diversification rates, remains a fundamental, but largely unanswered question in ecology and evolution. Here, we implement phylogenetic comparative analyses and ancestral area estimations in Radula, a liverwort genus of Cretaceous origin, to investigate the mechanisms that explain differences in geographical range size and diversification rates among lineages. Range size was phylogenetically constrained in the two sub-genera characterized by their almost complete Australasian and Neotropical endemicity, respectively. The congruence between the divergence time of these lineages and continental split suggests that plate tectonics could have played a major role in their present distribution, suggesting that a strong imprint of vicariance can still be found in extant distribution patterns in these highly mobile organisms. Amentuloradula, Volutoradula and Metaradula species did not appear to exhibit losses of dispersal capacities in terms of dispersal life-history traits, but evidence for significant phylogenetic signal in macroecological niche traits suggests that niche conservatism accounts for their restricted geographic ranges. Despite their greatly restricted distribution to Australasia and Neotropics respectively, Amentuloradula and Volutoradula did not exhibit significantly lower diversification rates than more widespread lineages, in contrast with the hypothesis that the probability of speciation increases with range size by promoting geographic isolation and increasing the rate at which novel habitats are encountered. We suggest that stochastic long-distance dispersal events may balance allele frequencies across large spatial scales, leading to low genetic structure among geographically distant areas or even continents, ultimately decreasing the diversification rates in highly mobile, widespread lineages.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Fifty-five Plagiochila species are recognized for Australia and New Zealand. Nine of these are new, all from Australia eight of which come from the Wet Tropics Bioregion of north east Queensland and ...one from the south-eastern mesic archipelago. Four of the new species belong in the challenging, and neglected, section Vagae. Three species are new Australian records, P. daviesiana, P. monospiris, and P. streimannii; and one species, P. alta, is a new record for New Zealand. Six species, P. annotina, P. circumdentata, P. colensoi, P. deltoidea, P. gigantea and P. ramosissima, are excluded from Australia as these are all New Zealand endemics reported in error for Australia. One New Zealand species is reported new for Australia (P. baylisii). Four species are excluded from Australia, P. furcata, P. inflata, P. renitens and P. sciophila, as they are based on misidentifications or are not supported by voucher material or both. Another interpretation of the confusion surrounding the name Plagiochila baileyana is presented, wherein Plagiochila baileyana is accepted as a species distinct from P. gigantea, while Plagiochila aculeata is returned to synonymy of P. fasciculata, and Plagiochila subfasciculata Colenso is reinstated. The number of Plagiochila species in Australia increases from 32 to 41, but the number of species in New Zealand decreases from 28 to 27 as a result of this study. New combinations at species level are also proposed for a variety of P. blepharophora from Fiji and two varieties of P. gymnoclada from Sumatra and Java, two species which morphological data suggests are grossly polyphyletic as currently circumscribed.
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