Bennett, K.D.
2004. Continuing the debate on the role of Quaternary environmental change for macroevolution..
Philosophical Transactions of the Royal Society of London Series B 359,
295-303.
The Quaternary has been a period of dramatic environmental change for
the past 1.8 Myr, with major shifts in distributions and abundances of
terrestrial and marine organisms. The evolutionary consequences of
this have been debated since the nineteenth century. However, the lack
of accurate relative and absolute time-scales for evolutions and
environmental change inhibited progress. We do now have an
understanding of time-scales. Palaeoecology has demonstrated the
individualistic nature of species' response to environmental change,
but lacks a means of determining ancestry. DNA characterization of
modern populations in relation to their distributions nicely
complements palaeoecological results by contributing ancestry. The
chance to understand how species originate and the causal factors of
speciation (environmental change or otherwise) may be within reach.
Bennett, K.D.
and Fuller, J.L. 2004. The mid-Holocene Tsuga canadensis (hemlock) decline, eastern North America - age versus causes: a reply to Payette.
The Holocene 14,
950-951.
A reply is made to comments by Payette (2004) concerning the paper
that attempted to determine the age of the Tsuga canadensis
decline in eastern North America (Bennett and Fuller, 2002). It is
pointed out that his criticisms of the methods used are all aspects
covered in the original paper, and which make little, if any,
difference to the result obtained. However, ecological aspects of the
decline were outside the scope of the paper.
Bennett, K.D.
2004. Out of Australasia?.
Quaternary Australasia 22,
5-7.
Giesecke, T. and
Bennett, K.D.
2004. The Holocene spread of Picea abies (L.) Kart. in Fennoscandia and adjacent areas.
Journal of Biogeography 31,
1523-1548.
Aim The Holocene spread of Picea abies in Fennoscandia is well
established from many sites and thus provides an opportunity for
detailed study of the dynamics of tree spread and population
expansion. Early- and mid-Holocene macrofossil evidence for presence
of P. abies in Fennoscandia has questioned traditional interpretations
of the timing and direction of its spread. This paper aims to
determine when, from where and by which pathways P. abies spread into
Fennoscandia. Understanding the character and dynamics of this spread
may give insight into the general understanding of Holocene tree
spread.
Location The north-western distribution of P. abies in
Europe, including Norway, Sweden, Finland, Estonia, Latvia, Lithuania,
north-western Russia, parts of Byelorussia and Poland.
Methods Holocene pollen diagrams with independent dating
control were collected from this region. The timing of the onset of
the continuous curve, the timing of the rise of the curve, the first
appearance of frequencies of 1%, 3%, 5%, and 10%, as well as timing
and the maximum amount of P. abies pollen, was obtained from these
pollen diagrams. A GIS analysis was used to display the data and
interpolate ages over the area under investigation.
Results Maps are presented showing a clear ESE to WNW trend in
the spread of P. abies for all characters interpolated. The timing of
the rise of the curve was difficult to use as sites east of the Baltic
have slowly rising P. abies frequencies while the western sites often
show a rapid rise.
Main conclusions The spread of P. abies in Fennoscandia and
adjacent areas can be separated into two phases: (i) A rapid early
Holocene spread out of Byelorussia and northern Russia at low
population density giving rise to small outpost populations, possibly
as far west as the Scandes Mountains. (ii) A mid- to late Holocene
front-like spread at high population densities moving from east to
west into the Baltic Republics and Finland, into northern Scandinavia
and then moving south and west towards its present-day distributional
limits.
Haberle, S.G. and
Bennett, K.D.
2004. Postglacial formation and dynamics of North Patagonian rainforest in the Chonos Archipelago, Southern Chile.
Quaternary Science Reviews 23, 2433-2452.
Pollen analysis of continuous sediment cores from two lakes in the
northern Chonos Archipelago (44°S) in southern Chile shows a complete
postglacial record of vegetation change. The fossil records indicate
that deglaciation was complete in the northern Chonos by at least
13,600 14C yr BP. Ericaceous heath and grassland persisted for more
than 600 years after deglaciation under the influence of dry/cold
climates and frequent
burning. Nothofagus-Pilgerodendron-Podocarpus
forest, with modern analogues in the southern Chonos Archipelago, was
established across the northern islands by 12,400 14C yr BP
under increasingly warm and wet climates. There is no evidence for a
return to cooler climates during the Younger Dryas chronozone. The
rise of Tepualia stipularis and Weinmannia trichosperma
as important forest components between 10,600 and 6000 14C
yr BP may be associated with climates that were warmer than
present. The collapse of Pilgerodendron communities during this
time may have been triggered by a combination of factors related to
disturbance frequency including tephra deposition events, fire and
climate change. After 6000 14C yr BP Pilgerodendron
recovers and Nothofagus-Pilgerodendron-Tepualia
forest persists until the present. European logging and burning
activity may have increased the susceptibility of North Patagonian
Rainforest to invasion by introduced species and to future collapse of
the long-lived Pilgerodendron communities. |