This discussion has really became very engrossing. I hope this trend of eflora continues. Promila
On Thu, Jul 29, 2010 at 6:12 PM, tanay bose <[email protected]> wrote: > Dear Sid Ji, > > Theory that I have put forward is simply my personal knowledge about > paleobiology, as I don’t have fossil records in my hand hence I have used > the word speculative. It is really wonderful to know that prominent > evolution biologists support the idea. Even many India famous Biologists > think my knowledge in Botany is also speculative (in negative sense), hence > you see speculation is term quite long standing for me. > > Analyses of the plastid *rbcL* gene played an early role in our evolving > understanding of legume phylogeny. Results from studies by two groups (e.g., > Käss and Wink, 1996, 1997; Doyle et al., 1997) were largely concordant with > earlier work, confirming for example the monophyly of smaller groups > suggested by other molecular evidence (e.g., Lavin et al., 1990; Sanderson > and Wojciechowski, 1996) or morphology (Chappill, 1995), and the monophyly > of the traditional subfamilies Mimosoideae (“mimosoids”) and Papilionoideae > (“papilionoids”), nested within a paraphyletic Caesalpinioideae > (“caesalpinioids”). Many of these groups have received additional support > and have been more clearly resolved by subsequent, more extensive studies > using the plastid *trnL* intron, alone or in combination with morphology > (e.g., Bruneau et al., 2001; Pennington et al., 2001; Herendeen et al., > 2003), the plastid *matK* gene and flanking *trnK* intron (e.g., Hu et > al., 2000; Luckow et al., 2003; Wojciechowski et al., 2004), the nuclear > ribosomal DNA ITS region (e.g., Sanderson and Wojciechowski, 1996; Allan and > Porter, 2000), or a combination of these and other molecular loci (Lavin et > al., 2001, 2003). > > The fossil record of the Fabaceae is abundant and diverse, particularly in > the Tertiary, with fossil flowers, fruits, leaflets, wood, and pollen known > from numerous localities; some examples are shown in the figures below > (Crepet and Taylor, 1985, 1986; Crepet and Herendeen, 1992; Herendeen, 1992; > Herendeen et al., 1992). Although there are several reports of earlier > fossils, *Sindora*-like pollen (subf. Caesalpinioideae) from the > Maastrichtian of Canada, Columbia, and Siberia (Raven and Polhill, 1981) and > woods similar to *Cassia* s. l. and Mimosoideae from the same time period > (e.g., Müller-Stoll and Mädel, 1967), they cannot be assigned unequivocally > to legumes. The first definitive legumes appear during the Late Paleocene > (ca. 56 Mya; Herendeen, 2001; Herendeen and Wing, 2001; Wing et al. 2004). > Representatives of all three traditionally recognized subfamilies, the > caesalpinioids, mimosoids, and papilionoids (Polhill et al., 1981), as well > as other taxonomically large clades within these subfamilies (e.g., > “genistoids”), are recorded from the fossil record soon afterward, beginning > around 50 to 55 Mya (e.g., Herendeen et al., 1992). Indeed, the occurrence > of diverse assemblages of taxa representing all three subfamilies at > multiple localities dating from the middle to upper Eocene, especially the > Mississippi Embayment of southeastern North America, suggests that most > major lineages of woody legumes (except for the tribe Cercideae) were > present and extensive diversification had taken place by this time > (Herendeen et al., 1992). > > Attempts to estimate the age of legumes and diversification in the family, > based on molecular sequence data, have been published in recent years. > Wikström et al. (2001) used a non-molecular clock based analysis of the > three gene data set (plastid *atpB* & *rbcL*, and nuclear 18S rDNA genes; > Soltis et al., 2000) with a minimum age of 84 Ma for the split between > Fagales and Cucurbitales as an internal calibration point, and estimated an > age for Fabaceae of 74-79 Ma. A comprehensive analysis of rates of molecular > evolution and estimated ages for crown groups within the legume family has > been presented by Lavin et al. (2005). In this study, Tertiary macrofossils > that showed distinctive combinations of apomorphic characters or features > were used to constrain the minimum age of 12 specific internal nodes to > estimate ages of a number of the clades identified in recent family-wide > phylogenetic analyses of plastid *matK* (Wojciechowski et al., 2004) and * > rbcL* (Kajita et al., 2001) gene sequence data. Their findings indicate > the age of the legume crown clade differs by only 1.0 to 2.5 Ma from the age > of the stem clade and the oldest caesalpinioid, mimosoid, and papilionoid > crown clades show approximately the same age range of 40 to 59 Ma, findings > consistent with a rapid diversification of the family soon after its origin > during the Late Paleocene. Remarkably, three large clades that include > papilionoids traditionally considered derived (Polhill et al., 1981; > Polhill, 1994), the “dalbergioids” (Lavin et al., 2001), “Hologalegina” > (Wojciechowski et al., 2000), and “mirbelioids” (Crisp et al., 2000), all > have ages estimates in the 50-Ma time frame or older. One of these, > Hologalegina, contains many of the well-known temperate, herbaceous species > of legumes grown as food and forage crops (e.g., alfalfa, clovers, peas, and > lentils). > > > > Adopted: Tree of Life Web Project [http://tolweb.org/Fabaceae/21093] > > > > > > Tanay > > > On Thu, Jul 29, 2010 at 5:12 PM, Pankaj Kumar <[email protected]>wrote: > >> Dear Sid, >> Thanks a lot for the clarification. I can make out that you have a >> good hold on understanding the studies on Molecular systematics. I >> would really be interested in knowing about your whereabouts to learn >> more from you as I dont know much abt this field and hence I would be >> interested in getting in touch with u. My email id is >> [email protected]. >> At the same time I really like Tanay's comments on, "If Heterostemon >> from upper Amazon has similarity then there should me some evidences >> in middle and lower Amazon in form of fossils for T indica, or any >> kind of transitional plant". My confusion was based on Heterostemon's >> origin in amazon...but lets see as said by him this theory is >> speculative and not affirmative and as said by you that it is >> possible. >> Lets say, may be due to inadequate sampling we cant reach to conclusion. >> Thanks again for putting up so much of info on a simple Tamarind!!!! >> This shows we still need to study hard each and every plant in our >> locality to understand every aspect of it. >> >> Nice....keep it up.... >> Regards >> Pankaj >> > > > > -- > Tanay Bose > +91(033) 25550676 (Resi) > 9830439691(Mobile) > > >
