[APWG] NEWS: Invasive Species Widespread, but Not More Than at Home

[Reinhart, Kurt]

Okay, I'll bite & also do some shameless self promotion.

A contrary view to Firn et al. is provided using a single species (a
prominent invasive tree species) that was carried out across 40 total
populations with slightly more than half in its native range and nearly
half in its non-native range in Reinhart et al. (2010, New Phytologist
http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.2009.03159.x/abst
ract).  This study concluded that measures of local relative abundance
were considerably greater in the non-native than native ranges.  This
study may not seem like a direct comparison because the main topic
relates to Enemy release but comparable data are in the supplement
(which apparently hasn't been read by many).  Others have made similar
observations though often without quantitative evidence for species like
spotted knapweed, garlic mustard, etc.

Firn et al's ELE study's main advantage over Reinhart et al.'s is their
use of considerably more species (26 species, 12 grass and 14 forb
species) at 39 sites.  They concluded species have similar levels of
abundance in native vs. non-native ranges.  A conclusion from their
paper is that many of the grasses were common at home and away while
many of the forbs were rare at home and away.  However based on
information in their supplement, I calculated that on average they have
measurements for only 2.5 sites per species in home ranges and 7.6 sites
per species in exotic ranges.  Sampling more species per region is
valued because many species have incredibly large distributions and
local abundances are variable throughout.  Sampling broadly is necessary
to avoid forms of regional sampling bias though researchers have to
balance logistics (also see Adams et al. 2009 as an example of an
extensive sampling network
(http://www.plantecology.org/Full%20text%20papers%20and%20abstracts/2009
%20papers/Adams%20Bioinvasions%202009.pdf).  Firn et al. help avoid this
limitation by looking at numerous species though more than half
represent relatively minor invasions.

I think what we would mostly like to know is what
traits/processes/interactions can we attribute to the success of the
most invasive species and whether their abundances, effects of enemies,
etc. differ at biogeographical scales.  Following the rule of 10s, these
species represent the most improbable invasion scenarios.  So we
shouldn't be too surprised if such rare events can never be predicted
without the benefit of hindsight.  However, I wouldn't be surprised if
further studies, focusing on highly invasive species which are the
exceptions, reveal that most/many are cases where the species attain
greater levels of local abundance/dominance in their non-native than
native ranges.  My 2 cents.  You decide.

Kurt Reinhart

  31. NEWS: Invasive Species Widespread,	but Not More Than at
Home
      Range (Olivia Kwong)
Message: 31
Date: Thu, 3 Mar 2011 08:27:30 -0600 (CST)
From: Olivia Kwong <plant at plantconservation.org>
To: apwg at lists.plantconservation.org
Subject: [APWG] NEWS: Invasive Species Widespread,	but Not More
Than
	at Home Range
Message-ID:
	<Pine.LNX.4.64.1103030826390.1121 at cpanel1-bb.epconline.net>
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http://www.sciencedaily.com/releases/2011/03/110301111459.htm

Invasive Species Widespread, but Not More Than at Home Range

ScienceDaily (Mar. 1, 2011) -- Invasive plant species have long had a 
reputation as being bad for a new ecosystem when they are introduced.

Stan Harpole, assistant professor of ecology, evolution and organismal 
biology at Iowa State University, is founding organizer of a team of
more 
than 70 researchers working at 65 sites worldwide that tested that 
assumption.

See the link above for the full article text.