[In each project category, projects are listed
as far as possible in reverse chronological order.]
Field-based projects (species
other than marine mammals)
Laboratory- or Home-based projects
Marine mammal projects (informed by
field experience)
Library / Critical-review projects
(some based on field observations)
(2001/2) Hansen, E.K. Examination of Dirona albolineata and
its endoparasitic copepod Ismailia in Barkley Sound, BC: analysis and
further studies.
Dirona is a nudibranch (a shell-less sea-snail) frequently, although apparently
not severely, parasitised by copepod crustaceans. This paper quantified
parasite load in a BC sample (collected and analyzed by the author while she
worked at the Bamfield Marine Station – www.bms.bc.ca
), and compared it with South Pacific and North Atlantic parallel cases. The
author expanded from these specific cases to argue that the Dirona/Ismailia
system might serve as an easily manipulable one for experimental testing of
evolutionary hypotheses about parasitism.
(2001) Fok, J. The effect of food
distribution on foraging behaviours in Glaucous-winged Gulls Larus
glaucescens.
Gulls were studied at Granville Island, Vancouver, BC, and were offered
food items differing only in distribution (clumped or dispersed). Adult gulls
did better by monopolizing clumped items, although many individuals present did
poorly; juvenile gulls were more successful when food was dispersed, and a
higher proportion of individuals gained food. This supports the view that
clumping promotes competition.
(1998/99)
Rudolf, U. A mark-recapture study of Rana aurorea on Bramham Island,
BC.
The author trapped red-legged frogs along two
stream-courses on Bramham Island as part of a broader research project of the
Coastal Ecosystem Research Foundation (CERF – www.cerf.bc.ca
), and evaluated habitat preferences as well as population density in the
process. The frogs preferred sunny sites with slow-flowing water and flat
banks; somewhat surprisingly neither water temperature, nor salinity (fairly
high in the lower reaches of these small streams), seemed to influence their
distribution.
(1996) Mackintosh, C. Time budgets of mallards Anas platyrhynchos
at disturbed and undisturbed urban sites: implications for wetland
conservation.
Mallards were observed using similar sampling
techniques at high-human-disturbance (Stanley Park), intermediate-disturbance
(Jericho Park), and low-disturbance (Burnaby Lake) sites in the Vancouver area.
Disturbances included human foot- and vehicle-traffic, the presence of
unconstrained dogs and children, and duck-feeding by humans. Mallards at the
high- and intermediate-disturbance sites spent less time foraging (their food
being supplied) and flying, but more time walking (lower-intensity escape
behaviour) and in sexual and agonistic behaviour, than mallards at the
low-disturbance site. Unless conservation areas are buffered from disturbance,
there is a possibility that duck behaviour could become too “tame” and leave
waterfowl vulnerable to predation and/or legal hunting or poaching, reducing
population viability.
(1996) Fonnesbeck, C.J. & A. Zuccolin. Borne on the wind: a study
on the reliability of scent-matching in drug-detector dogs.
In collaboration with
the Dog Squad of the Vancouver Police Department (VPD), the authors carried out
carefully controlled trials of marijuana scent-detection by police dogs,
trained to give a passive positive responses (sitting down adjacent to the
detected odour). The study was undertaken because the VPD could not obtain
search warrants for suspected marijuana-growing operations in city houses
without ‘probable cause’, and could not go onto private property to seek
‘probable cause’ (i.e., human-detected drug-scent): could dogs detect
scent reliably from the street? Using derelict buildings and small sachets of
marijuana, it was demonstrated that they could, and the technique was
subsequently used by the VPD with some success. The authors received a special
Citation of Merit from the Solicitor-General of Canada for their contribution
to effective law enforcement.
Back to start
of Field-based projects section
(2004) Pradhan, D. To fight or not to fight?
Factors influencing social behaviour in tiger barbs Capoeta tetrazona.
Tiger barbs are
well-known to be awkward fish for the home aquarium, with a reputation for
damaging other species of fish, or even each other, unless they are maintained
in large groups. This study attempted to tease out some factors that might be
responsible for these suppositions. The available volume of water had no impact
on the frequency of aggressive behaviours among tiger barbs. There was more
aggression when tiger barbs were stocked in larger groups (n=8) or in smaller
groups (n=2) than when they were in medium-size (n=4) groups, casting some
doubt on the folk wisdom of larger groups being best in mixed-species assemblages.
As individuals became more familiar with their neighbours, aggression
diminished; experimental isolation of individuals suggested that after a few
hours of isolation, they became more social in orientation. Much of tiger barb
social behaviour can probably be ascribed to hormonal balance changes evinced
by feedbacks from social interactions.
(2002) Foulkes, E. The influence of shoal size and species on
shoaling preference in two species of characid fish: the neon tetra Paracheirodon
innesi and the glowlight tetra Hemigrammus erythrozonus.
When offered the choice between staying alone
and joining a group, fish of each species preferred to join the group, of their
own species if possible, but of the other species if the “other-species” group
was substantially larger than the “own-species” group. This was surprising
given the morphological difference between the species (an “odd” fish would
probably be obvious to visually-hunting predators), but may have been due to
fish treating the observer as a predatory (immediately-threatening) stimulus.
(2001) Curtis, A. The effect of density and female presence on
sigmoid display, and density on male activity and/or chasing behaviour, in the
male Trinidadian guppy Poecilia reticulata.
Guppies exhibit internal fertilization, so
copulation requires the female’s “cooperation”, gained apparently when a female
is sufficiently stimulated by male display. Male guppies display frequently,
even when alone, or in the absence of females, but display much more when
females are present, and/or in larger-male-group conditions. Males also chase
each other (attempted display-displacements) more in larger groups. In natural
streams, where visibility is limited, males probably benefit from high activity
and attentiveness to the activity of other males, to find more females and thus
breeding opportunities.
(2001) Weir, J. The effect of handling
stress on the diving behaviour of two captive harbour seals Phoca vitulina.
[The author acknowledges the cooperation of
members of the Hochachka lab, Zoology Dept., UBC on this work.]
Harbour seals are frequently employed in
captive experiments, but little is known of their susceptibility to handling
stress. The author and colleagues observed seals before and after a stress-inducing
episode – sham manipulation similar to what would be encountered in
drug-injection protocols. The major difference in behaviour noted was a marked
decrease in the duration of dives after the stressor, an important observation
given that most research on pinnipeds is diving-related. The effect was
probably due to increased heartrate after stress (higher metabolic rate
shortening dive time), and a greater tendency for vigilance at the water
surface (to “check” for the continued presence of the stressor).
(2000) Dosanjh, R. Learned improvements in escape time in two species
of asteroids, Pisaster ochraceus and Solaster dawsoni.
Learning in
echinoderms has been little studied, but owing to the relative simplicity of
the echinoderm nervous system it may prove a useful research paradigm for the
control of learning. Seastars in the laboratory were constrained on a pegged
board, and their escape from the constraint was timed over several trials. Both
species improved their times, and both species tended to employ consistent
(arm-specific) movements to escape, suggesting learning. S. dawsoni
learned more effectively, presumably reflecting its role as a top-predator
species. Learning likely plays a part in guiding seastars in and out of the
intertidal zone in complex, rock-strewn habitats.
(1999) Jaibat, L. Behavioural changes in
hamsters after a period of fasting.
Fasting hamsters Mesocricetus
auratus were less active and less aggressive than provisioned hamsters, and
built bigger nests. This is similar to behaviour observed during bad weather
and low-food conditions in the field. Formerly-fasting individuals, when
returned to a normal ration, gathered food at the same rate as hamsters which
had not fasted, but hoarded, rather than immediately eating, most of the food
they collected. Such “precautionary” behaviour is analogous to preparation for
hibernation or estivation, states also triggered by perceived environmental
cues involving variation in food supply.
(1999) Murray, K.L. The phototaxic response of male Hemigrapsus
oregonensis to immersion and emersion in seawater.
Shore crabs offered habitat choices in a Y-maze
preferred a dark area to an illuminated one, whether they were in a dry or a
wet chamber. The preference was clearest in bright illumination, and less so in
dusky-light conditions (a time when many crab-predators might be expected to be
active), and brightly-lit crabs moved much more quickly to a dark shelter than
did those less brightly lit. Probably crabs are harder to see in dusky light,
so moving to a dark (protected) position may not be as important for them in
dim lighting; indeed, remaining motionless in dim light may be the optimal
choice.
(1998) Fraser, S. Changes in resting metabolic rate and behaviour due
to hyperthyroidism in harbour seals Phoca vitulina.
[The author acknowledges the cooperation of
members of the Hochachka lab, Zoology Dept., UBC on this work.]
Captive seals were evaluated before and after
administration of thyroid hormone for a range of physiological and behavioural
traits, as part of a larger research project. Hyperthyroid seals had elevated
metabolic rates, especially when ambient temperature was low (outdoor
facility), and exhibited higher locomotory activity (both terrestrial and
swimming) than euthyroid animals. Dive duration was also reduced by
hyperthyroidism, presumably a symptom of increased oxygen consumption compared
to the normally low consumption during diving. Thyroid activity is elevated
naturally in moulting animals, to compensate for loss of thermal control by
higher metabolic rate.
(1997) Zelichowska, A. Diving bradycardia during trained dives of
predetermined duration in harbour seals Phoca vitulina.
[The author acknowledges the cooperation of members of the Hochachka
lab, Zoology Dept., UBC on this work.]
Operant conditioning was used to train captive seals to make “Short” or
“Long” (five times longer than “Short”) dives on demand, with a characteristic
visual and auditory signal for each. Analysis of heartrate changes before and
during dives indicated that even from the beginning of a “Long” dive, the
animal was “aware” that the dive would indeed be prolonged: extensive slowing
of the heartrate normally associated with longer dives was seen immediately.
Thus learned cues enabled the seals to modify their physiological responses
and/or preparation for dive durations, a useful trait avoiding the necessity of
incurring oxygen-debt during longer immersions.
(1996) Samra. R. The effect of prior residency, relative carapace
size, and ability of Hemigrapsus oregonensis on resource holding
potential and territory defense.
Shore crabs compete for favourable foraging sites, places in which to
hide from predators, and other habitat features. What determines their success?
In a series of single-factor and multi-factor trials, it was determined that
larger crabs usually defeat (displace) smaller crabs, “able” (in possession of
the large claws, or chelae) crabs usually defeat “disabled” crabs, and
prior-resident (in a test-chamber) crabs usually defeat intruder (newly introduced)
crabs. Small residents often successfully repel larger intruders, and in
general all three traits – size, residency, and body-intactness – seem to
contribute to success or failure about equally.
(1995) Machado, E.M. The effect of prior exposure on aggressive
interactions in the jewel cichlid Hemichromis bimaculatus.
Cichlid fish are as a
rule territorial, and aggressive defenders of their territory. Pairs of fish
were exposed sequentially to each other and their aggressive biting behaviour
scored. Prior exposure to an individual was in some cases cause for increased
aggression in subsequent exposures, but generally not. Only fish which had
developed a bright red body-colouration (typical of the aggressive state)
reliably elicited such escalation in their opponents. In some cases where male
and female fish were exposed to each other, there was a significant decrease
in aggression over trials, probably indicative of pair-formation and imminent
mating interaction.
Back to
start of Laboratory- or Home-based projects section
(2005) Sellmann, T. Insight into the occurrence and
importance of ‘cheaters’ in the eastern North Pacific grey whale Eschrichtius
robustus.
[The author was one
of several UBC students participating in a jointly-conducted UBC/CERF (Coastal Ecosystem Research Foundation)
field course in July/August 2004 on the central coast of BC.]
Every year, most grey whales migrate along the west coast of North America, spending the summer months feeding in Aleutian waters and the winter breeding and calving in the subtropical lagoons of Baja California. A few individuals, however, do not make the full northern leg of the journey, and are categorized as “summer residents” on the BC/SE Alaska coastline. Presumably these individuals experience reduced travel costs (by shortening the journey) and perhaps reduced thermoregulatory costs (more northerly waters being somewhat cooler), but they also are likely to experience reduced feeding success (since the food sources are richer in the northern areas). Can this “partial migration” be a stable strategy in a fully-migrating population, and if so, how? The author uses a game-theoretic approach and estimates costs and benefits accruing to individuals of varying age classes, sexes, dominance-ranks, and health statuses, to formulate specific predictions about the likelihood of different categories of grey whales making different journey-lengths, then discusses how such analyses could be used as the foundation for recommendations on where to place marine protected areas.
(2005) Fisher, J. Semi-aquatic mammalian analogues of Eocene cetacean locomotor evolution: An energetics approach.
[The author was one
of several UBC students participating in a jointly-conducted UBC/CERF (Coastal Ecosystem Research Foundation)
field course in July/August 2004 on the central coast of BC.]
Fossil evidence from the most primitive cetaceans (and their terrestrial forebears, which have been described only in the last decade from discoveries in Pakistan) has been used to reconstruct possible pathways to specialized swimming behaviour. The underlying question has always been, why should terrestrial mammals ever have become obligate marine ones? Using modern methods of biomechanical analysis, this paper evaluates the energetic efficiency of walking (and other terrestrial gaits) as opposed to swimming (by paddling and whole-body flexion) in an extant amphibious mammal, the river otter Lutra canadensis. The paper also suggests how a wider range of modern mammals might be used as experimental analogues of various transitional forms known from fossils, in an attempt to test hypotheses favouring the evolution of aquatic locomotion.
(2005) Dennis, T. How grey whales swim and what happens when they lose their flukes.
[The author was one
of several UBC students participating in a jointly-conducted UBC/CERF (Coastal Ecosystem Research Foundation)
field course in July/August 2004 on the central coast of BC.]
This study was occasioned by the casual acquisition of data on cetaceans which survive in spite of physical handicaps such as damaged or missing tail-flukes. Firstly, the author outlines the biomechanics of buoyancy and thrust in swimming animals. Secondly, she focuses on the special structural and functional features of whale tails, and how swimming is organized and controlled in whales. Thirdly, she speculates on the mechanisms by which tail-loss without mortality might occur (swift trauma by accident, gradual necrosis after net-entanglement, birth defect compensated for by social-group care) and their likelihood. Lastly, the study assesses the ecological consequences of taillessness: reduced swimming and/or feeding efficiency (and thus higher energy consumption), effects on migration, predation-avoidance, and offspring-care.
(2005) Chen, K. Diving abilities of marine and terrestrial mammals: A behavioural or genetic adaptation?
[The author was one
of several UBC students participating in a jointly-conducted UBC/CERF (Coastal Ecosystem Research Foundation)
field course in July/August 2004 on the central coast of BC.]
This integrative project combines physiological processes, individual experience (training), and competing evolutionary constraints to evaluate the relative impact of proximate and ultimate factors on diving performance. Although all mammals share an underlying “dive response”, the weak response in terrestrial species may be only slightly modified with training. Obligate aquatic species like cetaceans have special cell-membrane architecture to resist compressive shape-change during deep dives, and extreme anoxia-tolerance in many body tissues, both traits clearly the result of evolutionary history. Amphibious species exhibit an intermediate state, so the author envisions critical testing of causal hypotheses about diving ability by raising such animals in different ways and measuring the effect of experience on trait expression.
(2005) Coyne, B. Pacific paradise: Examining grey whale evolution.
[The author was one
of several UBC students participating in a jointly-conducted UBC/CERF (Coastal Ecosystem Research Foundation)
field course in July/August 2004 on the central coast of BC.]
Grey whales Eschrichtius robustus are unusual members of the family of baleen (filter-feeding) whales, because rather than feeding on floating plankton in open water they have become specialized to scoop sediment and associated benthic prey items off the seafloor. Their range-limitation to the coastal waters of the NE Pacific basin, where such food-sources are abundant, is not too surprising… but how did grey whales reach this favoured habitat, and why should there be no populations in other areas of similar ecological conditions? The author describes the morphological and behavioural specializations of grey whales, examines palaeoclimatic and geologic data sets, and attempts to correlate these with the limited fossil record of baleen whales, in part to account for grey-whale history and in part to make recommendations for future investigations.
(2005) Allen, P. Seal herpes: Does it affect them down there?
[The author was one
of several UBC students participating in a jointly-conducted UBC/CERF (Coastal Ecosystem Research Foundation)
field course in July/August 2004 on the central coast of BC.]
Phocine herpes, caused by a virus taxonomically similar to those affecting other mammals, has become a growing problem in harbour seal Phoca vitulina populations of the North Pacific since 1994 (and elsewhere for longer). Up to 99% of individuals appear to carry the virus, though not all exhibit active symptoms (which include pneumonia, anorexia, diarrhea, and vomiting). One symptom potentially significant for the population’s persistence is adrenal-cortex necrosis (ACN); seals experiencing ACN cannot liberate glucose stores during dives because they lack adrenocortical hormone production, so their ability to forage for food is dramatically reduced. Because food-fish species preferred by seals are likely to be overharvested, and because pollutants already act in an immunosuppressive manner on wild seals, the currently slow-growing population of harbour seals could begin to decline with little warning in the near future.
(2005) Choi, J. Mechanics of diving amongst different taxa: Cetaceans, pinnipeds, and humans.
[The author was one
of several UBC students participating in a jointly-conducted UBC/CERF (Coastal Ecosystem Research Foundation)
field course in July/August 2004 on the central coast of BC.]
In all mammals there occurs upon submergence of the face an instinctive “dive reflex” involving breath-holding, bradycardia, and peripheral vasoconstriction. There is often also an enrichment of hematocrit by the release of erythrocytes from storage in the spleen. Among the more specialized marine mammals, in addition to strong development of the above traits, one observes very high levels of oxygen-storing myoglobin in muscle tissue. Although humans are not at all evolutionarily specialized for extended bouts of diving, individuals who undertake specialized training, such as sport-freedivers and East Asian shellfish-harvesters exhibit marked enhancement of diving capacity, suggesting that there is a substrate for diving specialization in any mammal, making the independent evolution of several lines of diving mammals somewhat less surprising.
(2004) Gorman, S. An investigation into polychlorinated biphenyl waste chemicals (PCBs) in the marine environment and their effects on the Arctic narwhal Monodon monoceros.
[The author was one
of several UBC students participating in a jointly-conducted UBC/CERF (Coastal Ecosystem Research Foundation)
field course in July/August 2004 on the central coast of BC.]
Many organic chemical residues are harmful toxins when released into the biosphere, and unfortunately laws controlling such releases are only occasionally respected. In this paper the author begins by describing the nature, sources, movements, and fates of polychlorinated biphenyls (PCBs). She then outlines the habitat, life history, and population status of the narwhal, which is a potential “test-case” species for Arctic pollution because of its diet, and the likelihood that PCBs will bioaccumulate in its extensive fatty tissue. She proceeds to design a comprehensive field study under which the risk to narwhals, and by extension to human and other Northern animal populations, could be estimated, with a view to new laws concerning public-health applications of this scientific knowledge.
(2003) Hofs, N. Some possible functional interpretations of sociogeographic variation in call structure of killer whales Orcinus orca on the west coast of North America.
[The author was one
of several UBC students participating in a jointly-conducted UBC/CERF (Coastal Ecosystem Research Foundation)
field course in July/August 2003 on the central coast of BC.]
Orcas occur in three sub-populations on the coast: “residents”
living in large groups near the coastline (two sets, one in northern BC and
Alaskan waters, and one in southern BC waters, eating mostly fish); “offshores”
living well off the coast and known to be genetically closely related to
residents (also eating fish); and “transients” living in small groups widely
scattered from Alaska to Mexico (eating mostly other marine mammals). Within
each sub-population, orcas are locally organized into matriarchal groups called
pods, which travel and hunt together. Probably the most striking variation
among the sub-populations is in the use of echo-location for hunting
(transients don’t use it, the others do); within each sub-population, there is
varying differentiation of call-sets among pods, verging on separate dialects.
To the extent that calls are used for communication, this situation is not
unlike the fragmentation and differentiation of human languages when groups are
isolated and calls become idiosyncratic.
(2003)
Marek, S. An amateur’s guide to assessing potential harm from the Acoustic
Thermometry of Ocean Climate (ATOC) project to marine mammals in the northeast
Pacific Ocean.
[The author was one
of several UBC students participating in a jointly-conducted UBC/CERF (Coastal Ecosystem Research Foundation)
field course in July/August 2003 on the central coast of BC.]
ATOC is one of
several research ventures seeking a better understanding of
temperature-patterns and other factors throughout the world’s oceans, partly
for the use of the US Navy, and because it involves the use of high-energy
sound-discharges as its probing-tool, it is likely to have impacts on organisms
and ecosystems. In order to evaluate the impacts, the author lays out first the
basic principles of acoustic physics as they relate to sound transmission under
water, then the various arguments and data-sets concerning the effect of sound
on organisms. Although there is insufficient data to be convincing, the
reliance of marine mammals in general (and cetaceans in particular) on sound
perception for all aspects of lifestyle appears to place them at direct risk in
high-noise conditions; indirect effects of sound (on fish and other
marine-mammal food sources) also need to be considered.
(1999/2000) Randall, D.A. Aspects of the behaviour and ecology of
grey whales Eschrichtius robustus off the Central Coast of mainland
British Columbia.
Using her own
observations and those made over the preceding five years by members of the
Coastal Ecosystem Research Foundation (CERF – www.cerf.bc.ca
), the author evaluated individual survival and population size, habitat use
patterns, and migrational timing of grey whales. A concentration of whales on
the best feeding sites in 1997/98 was presumptive evidence of the negative
effect of an El Niño event; this and other data were used to suggest criteria
for setting aside a Marine Protected Area on the Central Coast.
Back to start of marine mammal projects section
(2005)
Devery, L.S. Exotic commodities: An exploration into the exotic pet-trade
industry in North America.
The author makes use
of direct personal experiences working in wildlife-rehabilitation and sanctuaries
as a starting-point for a thorough and critical analysis of the trade in exotic
animal species. She begins by describing the sources of animals, how and why
they are moved from one place to another (and by whom), why animals become
unnecessary or superfluous, how animals are housed and maintained, and what
fates await them under a range of possible circumstances (species of animal,
age, breeding status, relative desirability in the trade, economic value,
endangered status, etc.). She then outlines the current local, national,
and international laws on the keeping and transfer of exotic animals, together
with the state of enforcement of these laws, licensing, treaty arrangements,
and other supposed controls on the trade. All through the paper, the degree to
which reasonable standards of animal welfare are applied is assessed, and
generally found wanting, while the predictive power of economic factors and
profitability proves almost invariably strong. In the final section, the author
attempts to outline practical means of reducing the trade, through public
education as well as political action to change laws, and makes predictions
about the likely outcomes for a range of species unless conditions change
dramatically.
(2003) MacDonald, A. Constructed wetlands
for onsite treatment of household greywater.
Current wastewater management in cities usually
involves the combination of all types of water-borne wastes – toilet waste,
clothes- and other washing-water, and rainwater/runoff – into a single stream.
This places a heavy and expensive burden on centralized waste-water processing
facilities, which are often overwhelmed by heavy rainstorms and may experience
a loss of containment of hazardous bacteria and toxic matter thereby. This
study designs a small plant- and decomposer-bacteria-based system suitable for
household (back-garden) use, for processing all but toilet water locally;
toilet waste would still require centralized disposal, but at a much lower
cost.
(2001) Young, L. The behavioural and
physiological basis of monogamy.
Mating systems and their determinants are major
topics of study in behavioural ecology, and the causation of human
mating-systems in particular is a subject of great interest to anthropologists
and sociologists as well as to biologists. This paper follows both these
threads, conducting a thorough review of the proposed theories, evaluating
empirical studies of them, and weighing the results. The main conclusion is
that no single theory accounts for all cases; some are best explained by
immediate survival benefits, others by social or historical constraints, and
still others by the overriding importance of physiological forces. Human
monogamy may be determined in a way similar to that in other species, or it may
be a merely convergent phenomenon with very different origins.
(2000) Beavington, L. The conservation implications of
population-dynamics of cheetah Acinonyx jubatus on the Serengeti Plains,
Tanzania.
The current cheetah population on the Serengeti
is unsustainable, given high offspring mortality relative to breeding rate.
This is mostly due to predation on cheetah cubs by lions, exacerbated by the
compression of several predator species into a small area (the Serengeti
National Park). These disquieting conclusions derive from an analysis of what
is known about cheetah biology and the management of the Serengeti region.
Because cheetahs thrive only in the absence of lions, the prospect for
maintaining both species is dismal; cheetahs may become museum-pieces (found
only in zoos) unless new conservation areas can be created for them, but with
the expanding human population of East Africa this seems unlikely.
(1999) Kuhrt, H. Camosun Bog: ecology, restoration, and an
observational study of Drosera rotundifolia.
This paper provides a
historical sketch of the Camosun Bog and how it has been modified by the
encroachment of human settlement in the past century. This analysis is placed
in context with a general survey of the hydrology and chemistry of bogs, and
how they form. Recommendations are made for how best to restore the current
degraded condition of the Bog, using the carnivorous sundew plant D.rotundifolia
as an indicator-species for bog-health (based on the author’s own study of the
plant’s distribution on site). This study was carried out in collaboration with
the Camosun Bog Restoration Committee, Greater Vancouver Regional District
Regional parks Department.
(1998) Trouth, M. The evolutionary
approaches to self-thinning in Impatiens capensis.
Self-thinning is the process by which the
density of seedling plants becomes adjusted over maturation time, often to a
deterministic final density of individuals of a given average size. The
mechanisms responsible for this widely observed phenomenon, however, are not
well characterized. Focussing on the widely studied annual impatiens plant, the
paper surveys models and tests of individualistic and group (altruistic) levels
of selection, competitive interactions, and the role of neighbourhood selection
(the patchy distribution of related individuals, allowing for context-dependency
in interactions), and concludes that all types of selection seem to play some
part in impatiens self-thinning.
Back
to start of Library / Critical-review projects section