Question: I understand that the first BLAST yields almost the same results as blastp. The second time the iterated blast generates different results as it uses different matrix based on our first result.

But I don't understand how exactly the second matrix is generated.

Answer: 
Ignoring for the moment the question of politics, let's consider the various definitions of the term "invasive species" that are in use. Colautti and MacIsaac write in their discussion of invasive species terminology ([1](http://www.esf.edu/efb/parry/502_reading/colautti2004.pdf)):

> 
> The greatest confusion [among the discussed ecological terms]
>  surrounds the common term ‘invasive’ and its various derivatives
>  (Richardson et al., 2000a). Explicit or implicit definitions for
>  ‘invasive’ include: (1) a synonym for ‘nonindigenous’ (e.g. Goodwin et
>  al., 1999; Radford &Cousens, 2000); (2) an adjective for native or
>  nonindigenous species (NIS) that have colonized natural areas (e.g.
>  Burke & Grime, 1996); (3) discrimination of NIS established in
>  cultivated habitats (as ‘noninvasive’) from those established in
>  natural habitats (e.g. Reichard & Hamilton, 1997); (4) NIS that are
>  widespread (e.g. van Clef & Stiles, 2001); or (5) widespread NIS that
>  have adverse effects on the invaded habitat (e.g. Davis & Thompson,
>  2000; Mack et al., 2000).
> 
> 
> 

Note that except for #2, all the definitions require that the species is a nonindigenous (non-native) species in the area under consideration. Therefore, while humans may be considered to have been an invasive species for much of our species history, under most definitions of the term **we no longer qualify because** except in a few places (mainly the arctic, antarctic and marine environments, where human presence is minimal) **we are now a native species.**

See also <http://www.smithsonianmag.com/science-nature/are-humans-an-invasive-species-42999965/?no-ist>
I don't think there is a good answer.

1. Many people and organisations do not even consider Homo sapiens when making such lists. Why? Because we have been for millennia a narcissistic species (think about religious narrative). This is similar to non-scientifically talking about animals. Homo sapiens is usually implicitly excluded from considerations.
2. Although Homo sapiens is present on all continents apart from Antarctica, Homo as a genus has been present for millions of years in Eurasia. Homo erectus has been there particularly long. Homo sapiens has outcompeted these species.
3. Ecosystems do change. Whether or not Homo sapiens is sufficiently long to be a native species is not a well posed question. Any answer would depend on arbitrary cutoffs. For instance if the first migration of Homo sapiens to Americas happened 14k years ago and it took 20 years per generation, then Americas are populated *only* for 700 generations. Is it a lot or is it little?
4. However, there are places in the world (mostly islands) where Homo sapiens settled very recently. Mauritius was first settled in 1638. And it is clear that since then many bird species (not only the famous dodo) went extinct and most of the area was converted from forests to sugar cane fields and towns. So yes, in this case there is no doubt the migration was recent and that it drastically changed the ecosystem, therefore it fulfils the definition.
5. Pragmatism. Probably the most important of it. We define invasive species for a reason: to give them a negative connotation and possibly plan a future removal. Doing these actions against humans are completely different from the legal point.

To sum up: a external observer would classify humans as an invasive species in at least some regions (Mauritius) and not in other (Africa south of Sahara). But people don't classify themselves as such because of political, moral, legal and pragmatic reasons.