Out of Africa: Biogeography and diversification of the pantropical pond skater genus Limnogonus Stål, 1868 (Hemiptera: Gerridae)

Gondwanan vicariance, long‐distance dispersal (LDD), and boreotropical migration have been proposed as alternative hypotheses explaining the pantropical distribution pattern of organisms. In this study, the historical biogeography of the pond skater genus Limnogonus was reconstructed to evaluate the impact of biogeographical scenarios in shaping their modern transoceanic disjunction. We sampled almost 65% of recognized Limnogonus species. Four DNA fragments including 69 sequences were used to reconstruct a phylogram. Divergence time was estimated using a Bayesian relaxed clock method and three fossil calibrations. Diversification dynamics and ancestral area reconstruction were investigated by using maximum likelihood and Bayesian approaches. Our results showed the crown group of Limnogonus originated and diversified in Africa in the early Eocene (49 Ma, HPD: 38–60 Ma), subsequently expanding into other regions via dispersal. The colonization of the New World originated from the Oriental Region probably via the Bering Land Bridge in the late Eocene. Two split events between the Old World and New World were identified: one between Neotropics and Oriental region around the middle Oligocene (30 Ma, HPD: 22–38 Ma), and the other between Neotropics and Africa during the middle Miocene (14 Ma, HPD: 8–21 Ma). The evolutionary history of Limnogonus involved two biogeographical processes. Gondwanan vicariance was not supported in our analyses. The diversification of Limnogonus among Africa, Oriental, and Neotropical regions corresponded with the age of land bridge connection and dispersed as a member associated with the broad boreotropical belt before local cooling (34 Ma). The current transoceanic disjunctions in Limnogonus could be better explained by the disruption of “mixed‐mesophytic” forest belt; however, the direct transoceanic LDD between the Neotropics and Africa could not be ruled out. In addition, the “LDD” model coupled with island hopping could be a reasonable explanation for the diversification of the Oriental and Australian regions during the Oligocene.     

Climate-influenced boreotropical survival and rampant introgressions explain the thriving of New World grapes in the north temperate zone

The north temperate region was characterized by a warm climate and a rich thermophilic flora before the Eocene, but early diversifications of the temperate biome under global climate change and biome shift remain uncertain. Moreover, it is becoming clear that hybridization/introgression is an important driving force of speciation in plant diversity. Here, we applied analyses from biogeography and phylogenetic networks to account for both introgression and incomplete lineage sorting based on geno...     

Biogeography of ‘tropical Anagallis’ (Myrsinaceae) inferred from nuclear and plastid DNA sequence data

Aim ‘Tropical Anagallis’ corresponds to one of two evolutionary lineages within the genus Anagallis L. Generally, species within this lineage have a limited distribution in (sub‐)tropical regions in Africa or Madagascar. Two species, however, are endemic to South America, and exhibit a trans‐Atlantic disjunction with the rest of the species within the lineage. To investigate this disjunct distribution, as well as other dispersal events, the distribution of extant taxa was used to hypothesize the ancestral area(s) of distribution. Location Africa, Madagascar, Europe and South America. Methods Dispersal–vicariance analysis (DIVA) was used to optimize distribution areas onto parsimony and Bayesian phylogenies based on sequence data from four chloroplast loci and the nuclear internal transcribed spacers (ITS). Results Parsimony analysis gave one most parsimonious tree while Bayesian analysis resulted in a collapsed node due to alternative placements of Anagallis nummularifolia Baker, endemic to Madagascar. Optimization of the present distribution using DIVA, and the most parsimonious tree and six alternative topologies of the Bayesian analysis, show an origin of the lineage in Europe as most likely, although one topology indicates a broader ancestral distribution area. Dispersal to Africa appears to have been a single event, while two parallel dispersal events seem to have resulted in the American as well as Madagascan distributions. Main conclusions The lineage ‘tropical Anagallis’ evolved in Europe and may have been present in the Eocene boreotropical forests, although scarcity of fossils makes assessment of age difficult. Dispersal to South America is proposed to have been via the North Atlantic land bridge, or, more likely, through transport by the North Equatorial Current. Dispersal from Europe to Africa represents a single event, while dispersal to Madagascar from mainland Africa has occurred twice.     

Early evolutionary history of the flowering plant family Annonaceae: steady diversification and boreotropical geodispersal

Aim Rain forest‐restricted plant families show disjunct distributions between the three major tropical regions: South America, Africa and Asia. Explaining these disjunctions has become an important challenge in biogeography. The pantropical plant family Annonaceae is used to test hypotheses that might explain diversification and distribution patterns in tropical biota: the museum hypothesis (low extinction leading to steady accumulation of species); and dispersal between Africa and Asia via Indian rafting versus boreotropical geodispersal. Location Tropics and boreotropics. Methods Molecular age estimates were calculated using a Bayesian approach based on 83% generic sampling representing all major lineages within the family, seven chloroplast markers and two fossil calibrations. An analysis of diversification was carried out, which included lineage‐through‐time (LTT) plots and the calculation of diversification rates for genera and major clades. Ancestral areas were reconstructed using a maximum likelihood approach that implements the dispersal–extinction–cladogenesis model. Results The LTT plots indicated a constant overall rate of diversification with low extinction rates for the family during the first 80 Ma of its existence. The highest diversification rates were inferred for several young genera such as Desmopsis, Uvariopsis and Unonopsis. A boreotropical migration route was supported over Indian rafting as the best fitting hypothesis to explain present‐day distribution patterns within the family. Main conclusions Early diversification within Annonaceae fits the hypothesis of a museum model of tropical diversification, with an overall steady increase in lineages possibly due to low extinction rates. The present‐day distribution of species within the two largest clades of Annonaceae is the result of two contrasting biogeographic histories. The ‘long‐branch clade’ has been diversifying since the beginning of the Cenozoic and underwent numerous geodispersals via the boreotropics and several more recent long‐distance dispersal events. In contrast, the ‘short‐branch clade’ dispersed once into Asia via the boreotropics during the Early Miocene and further dispersal was limited.     

Historical legacies in the geographical diversity patterns of New World palm (Arecaceae) subfamilies

The extent to which species richness patterns of the major palm subfamilies in the Americas are controlled by lineage history was studied. Based on the fossil record, we suggest that the subfamily Coryphoideae has followed a boreotropical dispersal route into Central and South America, whereas Calamoideae (tribe Lepidocaryeae), Ceroxyloideae and Arecoideae have Gondwana/South America-biased histories. However, Arecoideae has been present and diverse in both South and Central America at least since the early Tertiary. We used regression analyses to evaluate the relative importance of environmental factors and spatial variables (as substitutes for historical or other non-environmental factors) as determinants of geographical variation in species richness for each subfamily. Given the different lineage histories, we hypothesized that: (1) coryphoid richness should be least strongly controlled by the modern environment and exhibit a strong non-environmental bias towards Central and North America, reflecting its boreotropical invasion route, (2) calamoid species richness should exhibit a non-environmental bias towards South America, reflecting its long African–South American history, and (3) arecoid species richness should be most strongly environmentally determined, reflecting the long arecoid residency in both Central and South America. The regression analyses confirmed the hypothesized effects of lineage history on the geographical patterns in species richness. Hence, modern species richness patterns in the New World palm subfamilies strongly reflect their divergent biogeographical histories.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 113–125.     

Nichima gen. nov. (Alismataceae) based on reproductive structures from the Oligocene-Miocene of Mexico

Premise

Alismataceae, a sub-cosmopolitan family with ca. 17 genera and 113 species, is a large group of aquatic plants. Compression/impressions and bioinclusions of reproductive parts in amber support the documentation of the lineage in low-latitude North America. In Mexico, fossil aquatic plants have been infrequently documented. The new reproductive structures exhibit characteristics of Alismataceae, whose fossil record is mainly documented in the northern hemisphere through of fruits and seeds.

Methods

We described and compared 150 samples of reproductive structures preserved as impressions/compressions from the Oligocene Los Ahuehuetes locality in the state of Puebla, and two bioinclusions from the Miocene amber of Simojovel de Allende in the state of Chiapas, Mexico with extinct and extant taxa. Using a parsimony analysis based on 29 floral characters of 17 extant genera of the Alismataceae, we evaluated the relationship between the fossil material and potential living relatives.

Results

We discovered a new genus Nichima based on a perfect, actinomorphic flower with an expanded receptacle, three persistent sepals with multiple vasculatures, delicate and caducous petals, six stamens, and a gynoecium composed of three to more superior carpels, maturing into achenes. These characteristics resemble flowers of Alismataceae. Nichima represents an extinct member of the family, with two new species described here, Nichima magalloniae L. Hern., Cevallos-Ferriz et Hernández-Damián sp. nov. and Nichima gonzalez-medranoi L. Hern., Cevallos-Ferriz et Hernández-Damián, sp. nov. Their phylogenetic position suggests affinity with a clade that includes Baldiella, Echinodorus, and Alisma.

Conclusions

Reproductive structures from the Cenozoic of Mexico support the identification of a new extinct genus, Nichima, evidencing the extensive history of Alismataceae in North America's low latitudes and suggesting a southern extension of the boreotropical flora.