Early Cretaceous lineages of monocot flowering plants

Abstract

The phylogeny of flowering plants is now rapidly being disclosed by analysis of DNA sequence data, and currently, many Cretaceous fossils of flowering plants are being described. Combining molecular phylogenies with reference fossils of known minimum age makes it possible to date the nodes of the phylogenetic tree. The dating may be done by counting inferred changes in sequenced genes along the branches of the phylogeny and calculating change rates by using the reference fossils. Plastid DNA rbcL sequences and eight reference fossils indicate that approximately 14 of the extant monocot lineages may have diverged from each other during the Early Cretaceous >100 million years B.P. The lineages are very different in size and geographical distribution and provide perspective on flowering plant evolution.

Figure 1

Phylogeny of monocots with major clades that date back to the Early Cretaceous (>100 Myr B.P.). The nodes are arranged approximately by the age estimated from the branch lengths. Reference nodes A–H were used for calculating the change rates. The reference nodes have a minimum age given by the fossils (Table 1), and nodes B, C, F, and G are positioned accordingly. For nodes A, D, E, and H, the estimated age is greater, and they are thus arranged according to the age obtained from the mean branch length (Table 1) divided by the change rate (see text for calculation of change rates: node A 75/0.73 = 103 Myr, node D 85/0.73 = 116 Myr, node E 61/0.73 = 84 Myr, and node H 78/0.83 = 94 Myr). Confidence intervals (95%) for the datings of the basal nodes are indicated by gray bars. For complete circumscriptions of listed taxa see the current classification (6). Terminals are listed below with GenBank accession numbers in parentheses: 1 Acorus (M91625), 2 Tofieldia (AJ286562), 3 Gymnostachys (M91629, Araceae), 4 Pistia (M96963, Araceae), 5 Hydrocharis (U80701), 6 Butomus (U80685), 7 Alisma (L08759), 8 Limnocharis (U80717), 9 Aponogeton (U80684), 10 Scheuchzeria (U03728), 11 Posidonia (U80718), 12 Cymodocea (U80687), 13 Ruppia (U03729), 14 Triglochin (U80714, Juncaginaceae), 15 Potamogeton (L08765), 16 Zostera (U80734), 17 Vellozia (L19970), 18 Croomia (D28154, Stemonaceae), 19 Ludovia (L10251, Cyclanthaceae), 20 Pandanus (M91632), 21 Campynema (Z77264), 22 Trillium (D28164, Melanthiaceae), 23 Alstroemeria (Z77254), 24 Colchicum (L12673), 25 Luzuriaga (Z77300), 26 Lilium (L12682), 27 Smilax (D28333), 28 Philesia (Z77302), 29 Ripogonum (Z77309), 30 Narthecium (AJ286560), 31 Dioscorea (D28327), 32 Tacca (AJ286561), 33 Borya (Z77262), 34 Apostasia (Z73705, Orchidaceae), 35 Astelia (Z77261), 36 Blandfordia (Z7369), 37 Hypoxis (Z73702), 38 Lanaria (Z77313), 39 Tecophilaea (Z73709), 40 Doryanthes (Z73697), 41 Iris (L05037), 42 Ixiolirion (Z73704), 43 Xeronema (Z69235), 44 Xanthorrhoea (Z73710), 45 Convallaria (D28334), 46 Lomandra (L05039, Laxmanniaceae), 47 Allium (Z69204), 48 Agapanthus (Z69221), 49 Amaryllis (Z69219), 50 Asphodelus (Z73682), 51 Muilla (Z69213, Themidaceae), 52 Scilla (D2816, Hyacinthaceae), 53 Anemarrhena (Z77251), 54 Aphyllanthes (Z77259), 55 Asparagus (L05028), 56 Hemerocallis (L05036), 57 Behnia (Z69226), 58 Hosta (L10253, Agavaceae), 59 Anthericum (Z69225), 60 Herreria (Z69230), 61 Phoenix (M81814, Arecaceae), 62 Calectasia (AJ286557, Dasypogonaceae), 63 Philydrum (U41596), 64 Anigozanthes (AJ286556, Hemodoraceae), 65 Commelina (L05033), 66 Pontederia (U41597), 67 Marantochloa (L05453, Marantaceae), 68 Canna (L05445), 69 Musa (L05455), 70 Heliconia (L05451), 71 Zingiber (L05465), 72 Orchidantha (L05456, Lowiaceae), 73 Costus (L05447), 74 Strelitzia (L05461), 75 Ananas (L19977, Bromeliaceae), 76 Stegolepis (L19972, Rapateaceae), 77 Sparganium (M91633), 78 Typha (L05464), 79 Flagellaria (L12678), 80 Centrolepis (AJ286558), 81 Elegia (L12675, Restionaceae), 82 Bambusa (Poaceae) (M91626), 83 Ecdeiocolea (AJ286559), 84 Joinvillea (L01471), 85 Mayaca (AF036885), 86 Eriocaulon (L10252), 87 Xyris (AJ286563), 88 Thurnia (AF036881), 89 Prionium (U49223), 90 Cyperus (Y13016), and 91 Juncus (L12681).